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 <h3><a href="../contents.html">Table of Contents</a></h3>
 <ul>
<li><a class="reference internal" href="#">What’s New In Python 3.10</a><ul>
<li><a class="reference internal" href="#summary-release-highlights">Summary – Release highlights</a></li>
<li><a class="reference internal" href="#new-features">New Features</a><ul>
<li><a class="reference internal" href="#parenthesized-context-managers">Parenthesized context managers</a></li>
<li><a class="reference internal" href="#better-error-messages">Better error messages</a><ul>
<li><a class="reference internal" href="#syntaxerrors">SyntaxErrors</a></li>
<li><a class="reference internal" href="#indentationerrors">IndentationErrors</a></li>
<li><a class="reference internal" href="#attributeerrors">AttributeErrors</a></li>
<li><a class="reference internal" href="#nameerrors">NameErrors</a></li>
</ul>
</li>
<li><a class="reference internal" href="#pep-626-precise-line-numbers-for-debugging-and-other-tools">PEP 626: Precise line numbers for debugging and other tools</a></li>
<li><a class="reference internal" href="#pep-634-structural-pattern-matching">PEP 634: Structural Pattern Matching</a><ul>
<li><a class="reference internal" href="#syntax-and-operations">Syntax and operations</a></li>
<li><a class="reference internal" href="#declarative-approach">Declarative approach</a></li>
<li><a class="reference internal" href="#simple-pattern-match-to-a-literal">Simple pattern: match to a literal</a><ul>
<li><a class="reference internal" href="#behavior-without-the-wildcard">Behavior without the wildcard</a></li>
</ul>
</li>
<li><a class="reference internal" href="#patterns-with-a-literal-and-variable">Patterns with a literal and variable</a></li>
<li><a class="reference internal" href="#patterns-and-classes">Patterns and classes</a><ul>
<li><a class="reference internal" href="#patterns-with-positional-parameters">Patterns with positional parameters</a></li>
</ul>
</li>
<li><a class="reference internal" href="#nested-patterns">Nested patterns</a></li>
<li><a class="reference internal" href="#complex-patterns-and-the-wildcard">Complex patterns and the wildcard</a></li>
<li><a class="reference internal" href="#guard">Guard</a></li>
<li><a class="reference internal" href="#other-key-features">Other Key Features</a></li>
</ul>
</li>
<li><a class="reference internal" href="#optional-encodingwarning-and-encoding-locale-option">Optional <code class="docutils literal notranslate">EncodingWarning</code> and <code class="docutils literal notranslate">encoding=&quot;locale&quot;</code> option</a></li>
</ul>
</li>
<li><a class="reference internal" href="#new-features-related-to-type-hints">New Features Related to Type Hints</a><ul>
<li><a class="reference internal" href="#pep-604-new-type-union-operator">PEP 604: New Type Union Operator</a></li>
<li><a class="reference internal" href="#pep-612-parameter-specification-variables">PEP 612: Parameter Specification Variables</a></li>
<li><a class="reference internal" href="#pep-613-typealias">PEP 613: TypeAlias</a></li>
<li><a class="reference internal" href="#pep-647-user-defined-type-guards">PEP 647: User-Defined Type Guards</a></li>
</ul>
</li>
<li><a class="reference internal" href="#other-language-changes">Other Language Changes</a></li>
<li><a class="reference internal" href="#new-modules">New Modules</a></li>
<li><a class="reference internal" href="#improved-modules">Improved Modules</a><ul>
<li><a class="reference internal" href="#asyncio">asyncio</a></li>
<li><a class="reference internal" href="#argparse">argparse</a></li>
<li><a class="reference internal" href="#array">array</a></li>
<li><a class="reference internal" href="#asynchat-asyncore-smtpd">asynchat, asyncore, smtpd</a></li>
<li><a class="reference internal" href="#base64">base64</a></li>
<li><a class="reference internal" href="#bdb">bdb</a></li>
<li><a class="reference internal" href="#bisect">bisect</a></li>
<li><a class="reference internal" href="#codecs">codecs</a></li>
<li><a class="reference internal" href="#collections-abc">collections.abc</a></li>
<li><a class="reference internal" href="#contextlib">contextlib</a></li>
<li><a class="reference internal" href="#curses">curses</a></li>
<li><a class="reference internal" href="#dataclasses">dataclasses</a><ul>
<li><a class="reference internal" href="#slots">__slots__</a></li>
<li><a class="reference internal" href="#keyword-only-fields">Keyword-only fields</a></li>
</ul>
</li>
<li><a class="reference internal" href="#distutils">distutils</a></li>
<li><a class="reference internal" href="#doctest">doctest</a></li>
<li><a class="reference internal" href="#encodings">encodings</a></li>
<li><a class="reference internal" href="#fileinput">fileinput</a></li>
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<li><a class="reference internal" href="#idle-and-idlelib">IDLE and idlelib</a></li>
<li><a class="reference internal" href="#importlib-metadata">importlib.metadata</a></li>
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<li><a class="reference internal" href="#pprint">pprint</a></li>
<li><a class="reference internal" href="#py-compile">py_compile</a></li>
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<li><a class="reference internal" href="#types">types</a></li>
<li><a class="reference internal" href="#typing">typing</a></li>
<li><a class="reference internal" href="#unittest">unittest</a></li>
<li><a class="reference internal" href="#urllib-parse">urllib.parse</a></li>
<li><a class="reference internal" href="#xml">xml</a></li>
<li><a class="reference internal" href="#zipimport">zipimport</a></li>
</ul>
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<li><a class="reference internal" href="#optimizations">Optimizations</a></li>
<li><a class="reference internal" href="#deprecated">Deprecated</a></li>
<li><a class="reference internal" href="#removed">Removed</a></li>
<li><a class="reference internal" href="#porting-to-python-3-10">Porting to Python 3.10</a><ul>
<li><a class="reference internal" href="#changes-in-the-python-syntax">Changes in the Python syntax</a></li>
<li><a class="reference internal" href="#changes-in-the-python-api">Changes in the Python API</a></li>
<li><a class="reference internal" href="#changes-in-the-c-api">Changes in the C API</a></li>
</ul>
</li>
<li><a class="reference internal" href="#cpython-bytecode-changes">CPython bytecode changes</a></li>
<li><a class="reference internal" href="#build-changes">Build Changes</a></li>
<li><a class="reference internal" href="#c-api-changes">C API Changes</a><ul>
<li><a class="reference internal" href="#pep-652-maintaining-the-stable-abi">PEP 652: Maintaining the Stable ABI</a></li>
<li><a class="reference internal" href="#id1">New Features</a></li>
<li><a class="reference internal" href="#id2">Porting to Python 3.10</a></li>
<li><a class="reference internal" href="#id3">Deprecated</a></li>
<li><a class="reference internal" href="#id4">Removed</a></li>
</ul>
</li>
<li><a class="reference internal" href="#notable-security-feature-in-3-10-7">Notable security feature in 3.10.7</a></li>
<li><a class="reference internal" href="#notable-security-feature-in-3-10-8">Notable security feature in 3.10.8</a></li>
<li><a class="reference internal" href="#notable-changes-in-3-10-12">Notable Changes in 3.10.12</a><ul>
<li><a class="reference internal" href="#tarfile">tarfile</a></li>
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 <section id="what-s-new-in-python-3-10">
<h1>What’s New In Python 3.10<a class="headerlink" href="#what-s-new-in-python-3-10" title="Permalink to this headline">¶</a></h1>
<dl class="field-list simple">
<dt class="field-odd">Release</dt>
<dd class="field-odd">3.10.12
</dd>
<dt class="field-even">Date</dt>
<dd class="field-even">January 26, 2026
</dd>
<dt class="field-odd">Editor</dt>
<dd class="field-odd">Pablo Galindo Salgado
</dd>
</dl>
This article explains the new features in Python 3.10, compared to 3.9.
Python 3.10 was released on October 4, 2021.
For full details, see the <a class="reference internal" href="changelog.html#changelog">changelog</a>.
<section id="summary-release-highlights">
<h2>Summary – Release highlights<a class="headerlink" href="#summary-release-highlights" title="Permalink to this headline">¶</a></h2>
New syntax features:
<ul class="simple">
<li><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0634">PEP 634</a>, Structural Pattern Matching: Specification</li>
<li><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0635">PEP 635</a>, Structural Pattern Matching: Motivation and Rationale</li>
<li><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0636">PEP 636</a>, Structural Pattern Matching: Tutorial</li>
<li><a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=12782">bpo-12782</a>, Parenthesized context managers are now officially allowed.</li>
</ul>
New features in the standard library:
<ul class="simple">
<li><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0618">PEP 618</a>, Add Optional Length-Checking To zip.</li>
</ul>
Interpreter improvements:
<ul class="simple">
<li><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0626">PEP 626</a>, Precise line numbers for debugging and other tools.</li>
</ul>
New typing features:
<ul class="simple">
<li><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0604">PEP 604</a>, Allow writing union types as X | Y</li>
<li><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0612">PEP 612</a>, Parameter Specification Variables</li>
<li><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0613">PEP 613</a>, Explicit Type Aliases</li>
<li><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0647">PEP 647</a>, User-Defined Type Guards</li>
</ul>
Important deprecations, removals or restrictions:
<ul class="simple">
<li><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0644">PEP 644</a>, Require OpenSSL 1.1.1 or newer</li>
<li><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0632">PEP 632</a>, Deprecate distutils module.</li>
<li><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0623">PEP 623</a>, Deprecate and prepare for the removal of the wstr member in PyUnicodeObject.</li>
<li><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0624">PEP 624</a>, Remove Py_UNICODE encoder APIs</li>
<li><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0597">PEP 597</a>, Add optional EncodingWarning</li>
</ul>
</section>
<section id="new-features">
<h2>New Features<a class="headerlink" href="#new-features" title="Permalink to this headline">¶</a></h2>
<section id="parenthesized-context-managers">
<h3>Parenthesized context managers<a class="headerlink" href="#parenthesized-context-managers" title="Permalink to this headline">¶</a></h3>
Using enclosing parentheses for continuation across multiple lines
in context managers is now supported. This allows formatting a long
collection of context managers in multiple lines in a similar way
as it was previously possible with import statements. For instance,
all these examples are now valid:
<div class="highlight-python notranslate"><div class="highlight"><pre>with (CtxManager() as example):
 ...

with (
 CtxManager1(),
 CtxManager2()
):
 ...

with (CtxManager1(),
 CtxManager2() as example):
 ...

with (
 CtxManager1() as example1,
 CtxManager2() as example2
):
 ...
</pre></div>
</div>
it is also possible to use a trailing comma at the end of the
enclosed group:
<div class="highlight-python notranslate"><div class="highlight"><pre>with (
 CtxManager1() as example1,
 CtxManager2() as example2,
 CtxManager3() as example3,
):
 ...
</pre></div>
</div>
This new syntax uses the non LL(1) capacities of the new parser.
Check <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0617">PEP 617</a> for more details.
(Contributed by Guido van Rossum, Pablo Galindo and Lysandros Nikolaou
in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=12782">bpo-12782</a> and <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=40334">bpo-40334</a>.)
</section>
<section id="better-error-messages">
<h3>Better error messages<a class="headerlink" href="#better-error-messages" title="Permalink to this headline">¶</a></h3>
<section id="syntaxerrors">
<h4>SyntaxErrors<a class="headerlink" href="#syntaxerrors" title="Permalink to this headline">¶</a></h4>
When parsing code that contains unclosed parentheses or brackets the interpreter
now includes the location of the unclosed bracket of parentheses instead of displaying
SyntaxError: unexpected EOF while parsing or pointing to some incorrect location.
For instance, consider the following code (notice the unclosed ‘{‘):
<div class="highlight-python notranslate"><div class="highlight"><pre>expected = {9: 1, 18: 2, 19: 2, 27: 3, 28: 3, 29: 3, 36: 4, 37: 4,
 38: 4, 39: 4, 45: 5, 46: 5, 47: 5, 48: 5, 49: 5, 54: 6,
some_other_code = foo()
</pre></div>
</div>
Previous versions of the interpreter reported confusing places as the location of
the syntax error:
<div class="highlight-python notranslate"><div class="highlight"><pre>File &quot;example.py&quot;, line 3
 some_other_code = foo()
 ^
SyntaxError: invalid syntax
</pre></div>
</div>
but in Python 3.10 a more informative error is emitted:
<div class="highlight-python notranslate"><div class="highlight"><pre>File &quot;example.py&quot;, line 1
 expected = {9: 1, 18: 2, 19: 2, 27: 3, 28: 3, 29: 3, 36: 4, 37: 4,
 ^
SyntaxError: &#39;{&#39; was never closed
</pre></div>
</div>
In a similar way, errors involving unclosed string literals (single and triple
quoted) now point to the start of the string instead of reporting EOF/EOL.
These improvements are inspired by previous work in the PyPy interpreter.
(Contributed by Pablo Galindo in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42864">bpo-42864</a> and Batuhan Taskaya in
<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=40176">bpo-40176</a>.)
<a class="reference internal" href="../library/exceptions.html#SyntaxError" title="SyntaxError"><code class="xref py py-exc docutils literal notranslate">SyntaxError</code></a> exceptions raised by the interpreter will now highlight the
full error range of the expression that constitutes the syntax error itself,
instead of just where the problem is detected. In this way, instead of displaying
(before Python 3.10):
<div class="highlight-python notranslate"><div class="highlight"><pre>&gt;&gt;&gt; foo(x, z for z in range(10), t, w)
 File &quot;&lt;stdin&gt;&quot;, line 1
 foo(x, z for z in range(10), t, w)
 ^
SyntaxError: Generator expression must be parenthesized
</pre></div>
</div>
now Python 3.10 will display the exception as:
<div class="highlight-python notranslate"><div class="highlight"><pre>&gt;&gt;&gt; foo(x, z for z in range(10), t, w)
 File &quot;&lt;stdin&gt;&quot;, line 1
 foo(x, z for z in range(10), t, w)
 ^^^^^^^^^^^^^^^^^^^^
SyntaxError: Generator expression must be parenthesized
</pre></div>
</div>
This improvement was contributed by Pablo Galindo in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43914">bpo-43914</a>.
A considerable amount of new specialized messages for <a class="reference internal" href="../library/exceptions.html#SyntaxError" title="SyntaxError"><code class="xref py py-exc docutils literal notranslate">SyntaxError</code></a> exceptions
have been incorporated. Some of the most notable ones are as follows:
<ul>
<li>Missing <code class="docutils literal notranslate">:</code> before blocks:
<blockquote>
<div><div class="highlight-python notranslate"><div class="highlight"><pre>&gt;&gt;&gt; if rocket.position &gt; event_horizon
 File &quot;&lt;stdin&gt;&quot;, line 1
 if rocket.position &gt; event_horizon
 ^
SyntaxError: expected &#39;:&#39;
</pre></div>
</div>
(Contributed by Pablo Galindo in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42997">bpo-42997</a>.)
</div></blockquote>
</li>
<li>Unparenthesised tuples in comprehensions targets:
<blockquote>
<div><div class="highlight-python notranslate"><div class="highlight"><pre>&gt;&gt;&gt; {x,y for x,y in zip(&#39;abcd&#39;, &#39;1234&#39;)}
 File &quot;&lt;stdin&gt;&quot;, line 1
 {x,y for x,y in zip(&#39;abcd&#39;, &#39;1234&#39;)}
 ^
SyntaxError: did you forget parentheses around the comprehension target?
</pre></div>
</div>
(Contributed by Pablo Galindo in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43017">bpo-43017</a>.)
</div></blockquote>
</li>
<li>Missing commas in collection literals and between expressions:
<blockquote>
<div><div class="highlight-python notranslate"><div class="highlight"><pre>&gt;&gt;&gt; items = {
... x: 1,
... y: 2
... z: 3,
 File &quot;&lt;stdin&gt;&quot;, line 3
 y: 2
 ^
SyntaxError: invalid syntax. Perhaps you forgot a comma?
</pre></div>
</div>
(Contributed by Pablo Galindo in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43822">bpo-43822</a>.)
</div></blockquote>
</li>
<li>Multiple Exception types without parentheses:
<blockquote>
<div><div class="highlight-python notranslate"><div class="highlight"><pre>&gt;&gt;&gt; try:
... build_dyson_sphere()
... except NotEnoughScienceError, NotEnoughResourcesError:
 File &quot;&lt;stdin&gt;&quot;, line 3
 except NotEnoughScienceError, NotEnoughResourcesError:
 ^
SyntaxError: multiple exception types must be parenthesized
</pre></div>
</div>
(Contributed by Pablo Galindo in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43149">bpo-43149</a>.)
</div></blockquote>
</li>
<li>Missing <code class="docutils literal notranslate">:</code> and values in dictionary literals:
<blockquote>
<div><div class="highlight-python notranslate"><div class="highlight"><pre>&gt;&gt;&gt; values = {
... x: 1,
... y: 2,
... z:
... }
 File &quot;&lt;stdin&gt;&quot;, line 4
 z:
 ^
SyntaxError: expression expected after dictionary key and &#39;:&#39;

&gt;&gt;&gt; values = {x:1, y:2, z w:3}
 File &quot;&lt;stdin&gt;&quot;, line 1
 values = {x:1, y:2, z w:3}
 ^
SyntaxError: &#39;:&#39; expected after dictionary key
</pre></div>
</div>
(Contributed by Pablo Galindo in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43823">bpo-43823</a>.)
</div></blockquote>
</li>
<li><code class="docutils literal notranslate">try</code> blocks without <code class="docutils literal notranslate">except</code> or <code class="docutils literal notranslate">finally</code> blocks:
<blockquote>
<div><div class="highlight-python notranslate"><div class="highlight"><pre>&gt;&gt;&gt; try:
... x = 2
... something = 3
 File &quot;&lt;stdin&gt;&quot;, line 3
 something = 3
 ^^^^^^^^^
SyntaxError: expected &#39;except&#39; or &#39;finally&#39; block
</pre></div>
</div>
(Contributed by Pablo Galindo in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=44305">bpo-44305</a>.)
</div></blockquote>
</li>
<li>Usage of <code class="docutils literal notranslate">=</code> instead of <code class="docutils literal notranslate">==</code> in comparisons:
<blockquote>
<div><div class="highlight-python notranslate"><div class="highlight"><pre>&gt;&gt;&gt; if rocket.position = event_horizon:
 File &quot;&lt;stdin&gt;&quot;, line 1
 if rocket.position = event_horizon:
 ^
SyntaxError: cannot assign to attribute here. Maybe you meant &#39;==&#39; instead of &#39;=&#39;?
</pre></div>
</div>
(Contributed by Pablo Galindo in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43797">bpo-43797</a>.)
</div></blockquote>
</li>
<li>Usage of <code class="docutils literal notranslate">*</code> in f-strings:
<blockquote>
<div><div class="highlight-python notranslate"><div class="highlight"><pre>&gt;&gt;&gt; f&quot;Black holes {*all_black_holes} and revelations&quot;
 File &quot;&lt;stdin&gt;&quot;, line 1
 (*all_black_holes)
 ^
SyntaxError: f-string: cannot use starred expression here
</pre></div>
</div>
(Contributed by Pablo Galindo in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41064">bpo-41064</a>.)
</div></blockquote>
</li>
</ul>
</section>
<section id="indentationerrors">
<h4>IndentationErrors<a class="headerlink" href="#indentationerrors" title="Permalink to this headline">¶</a></h4>
Many <a class="reference internal" href="../library/exceptions.html#IndentationError" title="IndentationError"><code class="xref py py-exc docutils literal notranslate">IndentationError</code></a> exceptions now have more context regarding what kind of block
was expecting an indentation, including the location of the statement:
<div class="highlight-python notranslate"><div class="highlight"><pre>&gt;&gt;&gt; def foo():
... if lel:
... x = 2
 File &quot;&lt;stdin&gt;&quot;, line 3
 x = 2
 ^
IndentationError: expected an indented block after &#39;if&#39; statement in line 2
</pre></div>
</div>
</section>
<section id="attributeerrors">
<h4>AttributeErrors<a class="headerlink" href="#attributeerrors" title="Permalink to this headline">¶</a></h4>
When printing <a class="reference internal" href="../library/exceptions.html#AttributeError" title="AttributeError"><code class="xref py py-exc docutils literal notranslate">AttributeError</code></a>, <code class="xref c c-func docutils literal notranslate">PyErr_Display()</code> will offer
suggestions of similar attribute names in the object that the exception was
raised from:
<div class="highlight-python notranslate"><div class="highlight"><pre>&gt;&gt;&gt; collections.namedtoplo
Traceback (most recent call last):
 File &quot;&lt;stdin&gt;&quot;, line 1, in &lt;module&gt;
AttributeError: module &#39;collections&#39; has no attribute &#39;namedtoplo&#39;. Did you mean: namedtuple?
</pre></div>
</div>
(Contributed by Pablo Galindo in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=38530">bpo-38530</a>.)
<blockquote>
<div><div class="admonition warning">
Warning
Notice this won’t work if <code class="xref c c-func docutils literal notranslate">PyErr_Display()</code> is not called to display the error
which can happen if some other custom error display function is used. This is a common
scenario in some REPLs like IPython.
</div>
</div></blockquote>
</section>
<section id="nameerrors">
<h4>NameErrors<a class="headerlink" href="#nameerrors" title="Permalink to this headline">¶</a></h4>
When printing <a class="reference internal" href="../library/exceptions.html#NameError" title="NameError"><code class="xref py py-exc docutils literal notranslate">NameError</code></a> raised by the interpreter, <code class="xref c c-func docutils literal notranslate">PyErr_Display()</code>
will offer suggestions of similar variable names in the function that the exception
was raised from:
<div class="highlight-python notranslate"><div class="highlight"><pre>&gt;&gt;&gt; schwarzschild_black_hole = None
&gt;&gt;&gt; schwarschild_black_hole
Traceback (most recent call last):
 File &quot;&lt;stdin&gt;&quot;, line 1, in &lt;module&gt;
NameError: name &#39;schwarschild_black_hole&#39; is not defined. Did you mean: schwarzschild_black_hole?
</pre></div>
</div>
(Contributed by Pablo Galindo in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=38530">bpo-38530</a>.)
<blockquote>
<div><div class="admonition warning">
Warning
Notice this won’t work if <code class="xref c c-func docutils literal notranslate">PyErr_Display()</code> is not called to display the error,
which can happen if some other custom error display function is used. This is a common
scenario in some REPLs like IPython.
</div>
</div></blockquote>
</section>
</section>
<section id="pep-626-precise-line-numbers-for-debugging-and-other-tools">
<h3>PEP 626: Precise line numbers for debugging and other tools<a class="headerlink" href="#pep-626-precise-line-numbers-for-debugging-and-other-tools" title="Permalink to this headline">¶</a></h3>
PEP 626 brings more precise and reliable line numbers for debugging, profiling and coverage tools.
Tracing events, with the correct line number, are generated for all lines of code executed and only for lines of code that are executed.
The <code class="docutils literal notranslate">f_lineno</code> attribute of frame objects will always contain the expected line number.
The <code class="docutils literal notranslate">co_lnotab</code> attribute of code objects is deprecated and will be removed in 3.12.
Code that needs to convert from offset to line number should use the new <code class="docutils literal notranslate">co_lines()</code> method instead.
</section>
<section id="pep-634-structural-pattern-matching">
<h3>PEP 634: Structural Pattern Matching<a class="headerlink" href="#pep-634-structural-pattern-matching" title="Permalink to this headline">¶</a></h3>
Structural pattern matching has been added in the form of a match statement
and case statements of patterns with associated actions. Patterns
consist of sequences, mappings, primitive data types as well as class instances.
Pattern matching enables programs to extract information from complex data types,
branch on the structure of data, and apply specific actions based on different
forms of data.
<section id="syntax-and-operations">
<h4>Syntax and operations<a class="headerlink" href="#syntax-and-operations" title="Permalink to this headline">¶</a></h4>
The generic syntax of pattern matching is:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>match subject:
 case &lt;pattern_1&gt;:
 &lt;action_1&gt;
 case &lt;pattern_2&gt;:
 &lt;action_2&gt;
 case &lt;pattern_3&gt;:
 &lt;action_3&gt;
 case _:
 &lt;action_wildcard&gt;
</pre></div>
</div>
A match statement takes an expression and compares its value to successive
patterns given as one or more case blocks. Specifically, pattern matching
operates by:
<blockquote>
<div><ol class="arabic simple">
<li>using data with type and shape (the <code class="docutils literal notranslate">subject</code>)</li>
<li>evaluating the <code class="docutils literal notranslate">subject</code> in the <code class="docutils literal notranslate">match</code> statement</li>
<li>comparing the subject with each pattern in a <code class="docutils literal notranslate">case</code> statement
from top to bottom until a match is confirmed.</li>
<li>executing the action associated with the pattern of the confirmed
match</li>
<li>If an exact match is not confirmed, the last case, a wildcard <code class="docutils literal notranslate">_</code>,
if provided, will be used as the matching case. If an exact match is
not confirmed and a wildcard case does not exist, the entire match
block is a no-op.</li>
</ol>
</div></blockquote>
</section>
<section id="declarative-approach">
<h4>Declarative approach<a class="headerlink" href="#declarative-approach" title="Permalink to this headline">¶</a></h4>
Readers may be aware of pattern matching through the simple example of matching
a subject (data object) to a literal (pattern) with the switch statement found
in C, Java or JavaScript (and many other languages). Often the switch statement
is used for comparison of an object/expression with case statements containing
literals.
More powerful examples of pattern matching can be found in languages such as
Scala and Elixir. With structural pattern matching, the approach is “declarative” and
explicitly states the conditions (the patterns) for data to match.
While an “imperative” series of instructions using nested “if” statements
could be used to accomplish something similar to structural pattern matching,
it is less clear than the “declarative” approach. Instead the “declarative”
approach states the conditions to meet for a match and is more readable through
its explicit patterns. While structural pattern matching can be used in its
simplest form comparing a variable to a literal in a case statement, its
true value for Python lies in its handling of the subject’s type and shape.
</section>
<section id="simple-pattern-match-to-a-literal">
<h4>Simple pattern: match to a literal<a class="headerlink" href="#simple-pattern-match-to-a-literal" title="Permalink to this headline">¶</a></h4>
Let’s look at this example as pattern matching in its simplest form: a value,
the subject, being matched to several literals, the patterns. In the example
below, <code class="docutils literal notranslate">status</code> is the subject of the match statement. The patterns are
each of the case statements, where literals represent request status codes.
The associated action to the case is executed after a match:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>def http_error(status):
 match status:
 case 400:
 return &quot;Bad request&quot;
 case 404:
 return &quot;Not found&quot;
 case 418:
 return &quot;I&#39;m a teapot&quot;
 case _:
 return &quot;Something&#39;s wrong with the internet&quot;
</pre></div>
</div>
If the above function is passed a <code class="docutils literal notranslate">status</code> of 418, “I’m a teapot” is returned.
If the above function is passed a <code class="docutils literal notranslate">status</code> of 500, the case statement with
<code class="docutils literal notranslate">_</code> will match as a wildcard, and “Something’s wrong with the internet” is
returned.
Note the last block: the variable name, <code class="docutils literal notranslate">_</code>, acts as a wildcard and insures
the subject will always match. The use of <code class="docutils literal notranslate">_</code> is optional.
You can combine several literals in a single pattern using <code class="docutils literal notranslate">|</code> (“or”):
<div class="highlight-python3 notranslate"><div class="highlight"><pre>case 401 | 403 | 404:
 return &quot;Not allowed&quot;
</pre></div>
</div>
<section id="behavior-without-the-wildcard">
<h5>Behavior without the wildcard<a class="headerlink" href="#behavior-without-the-wildcard" title="Permalink to this headline">¶</a></h5>
If we modify the above example by removing the last case block, the example
becomes:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>def http_error(status):
 match status:
 case 400:
 return &quot;Bad request&quot;
 case 404:
 return &quot;Not found&quot;
 case 418:
 return &quot;I&#39;m a teapot&quot;
</pre></div>
</div>
Without the use of <code class="docutils literal notranslate">_</code> in a case statement, a match may not exist. If no
match exists, the behavior is a no-op. For example, if <code class="docutils literal notranslate">status</code> of 500 is
passed, a no-op occurs.
</section>
</section>
<section id="patterns-with-a-literal-and-variable">
<h4>Patterns with a literal and variable<a class="headerlink" href="#patterns-with-a-literal-and-variable" title="Permalink to this headline">¶</a></h4>
Patterns can look like unpacking assignments, and a pattern may be used to bind
variables. In this example, a data point can be unpacked to its x-coordinate
and y-coordinate:
<div class="highlight-python3 notranslate"><div class="highlight"><pre># point is an (x, y) tuple
match point:
 case (0, 0):
 print(&quot;Origin&quot;)
 case (0, y):
 print(f&quot;Y={y}&quot;)
 case (x, 0):
 print(f&quot;X={x}&quot;)
 case (x, y):
 print(f&quot;X={x}, Y={y}&quot;)
 case _:
 raise ValueError(&quot;Not a point&quot;)
</pre></div>
</div>
The first pattern has two literals, <code class="docutils literal notranslate">(0, 0)</code>, and may be thought of as an
extension of the literal pattern shown above. The next two patterns combine a
literal and a variable, and the variable binds a value from the subject
(<code class="docutils literal notranslate">point</code>). The fourth pattern captures two values, which makes it
conceptually similar to the unpacking assignment <code class="docutils literal notranslate">(x, y) = point</code>.
</section>
<section id="patterns-and-classes">
<h4>Patterns and classes<a class="headerlink" href="#patterns-and-classes" title="Permalink to this headline">¶</a></h4>
If you are using classes to structure your data, you can use as a pattern
the class name followed by an argument list resembling a constructor. This
pattern has the ability to capture class attributes into variables:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>class Point:
 x: int
 y: int

def location(point):
 match point:
 case Point(x=0, y=0):
 print(&quot;Origin is the point&#39;s location.&quot;)
 case Point(x=0, y=y):
 print(f&quot;Y={y} and the point is on the y-axis.&quot;)
 case Point(x=x, y=0):
 print(f&quot;X={x} and the point is on the x-axis.&quot;)
 case Point():
 print(&quot;The point is located somewhere else on the plane.&quot;)
 case _:
 print(&quot;Not a point&quot;)
</pre></div>
</div>
<section id="patterns-with-positional-parameters">
<h5>Patterns with positional parameters<a class="headerlink" href="#patterns-with-positional-parameters" title="Permalink to this headline">¶</a></h5>
You can use positional parameters with some builtin classes that provide an
ordering for their attributes (e.g. dataclasses). You can also define a specific
position for attributes in patterns by setting the <code class="docutils literal notranslate">__match_args__</code> special
attribute in your classes. If it’s set to (“x”, “y”), the following patterns
are all equivalent (and all bind the <code class="docutils literal notranslate">y</code> attribute to the <code class="docutils literal notranslate">var</code> variable):
<div class="highlight-python3 notranslate"><div class="highlight"><pre>Point(1, var)
Point(1, y=var)
Point(x=1, y=var)
Point(y=var, x=1)
</pre></div>
</div>
</section>
</section>
<section id="nested-patterns">
<h4>Nested patterns<a class="headerlink" href="#nested-patterns" title="Permalink to this headline">¶</a></h4>
Patterns can be arbitrarily nested. For example, if our data is a short
list of points, it could be matched like this:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>match points:
 case []:
 print(&quot;No points in the list.&quot;)
 case [Point(0, 0)]:
 print(&quot;The origin is the only point in the list.&quot;)
 case [Point(x, y)]:
 print(f&quot;A single point {x}, {y} is in the list.&quot;)
 case [Point(0, y1), Point(0, y2)]:
 print(f&quot;Two points on the Y axis at {y1}, {y2} are in the list.&quot;)
 case _:
 print(&quot;Something else is found in the list.&quot;)
</pre></div>
</div>
</section>
<section id="complex-patterns-and-the-wildcard">
<h4>Complex patterns and the wildcard<a class="headerlink" href="#complex-patterns-and-the-wildcard" title="Permalink to this headline">¶</a></h4>
To this point, the examples have used <code class="docutils literal notranslate">_</code> alone in the last case statement.
A wildcard can be used in more complex patterns, such as <code class="docutils literal notranslate">('error', code, _)</code>.
For example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>match test_variable:
 case (&#39;warning&#39;, code, 40):
 print(&quot;A warning has been received.&quot;)
 case (&#39;error&#39;, code, _):
 print(f&quot;An error {code} occurred.&quot;)
</pre></div>
</div>
In the above case, <code class="docutils literal notranslate">test_variable</code> will match for (‘error’, code, 100) and
(‘error’, code, 800).
</section>
<section id="guard">
<h4>Guard<a class="headerlink" href="#guard" title="Permalink to this headline">¶</a></h4>
We can add an <code class="docutils literal notranslate">if</code> clause to a pattern, known as a “guard”. If the
guard is false, <code class="docutils literal notranslate">match</code> goes on to try the next case block. Note
that value capture happens before the guard is evaluated:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>match point:
 case Point(x, y) if x == y:
 print(f&quot;The point is located on the diagonal Y=X at {x}.&quot;)
 case Point(x, y):
 print(f&quot;Point is not on the diagonal.&quot;)
</pre></div>
</div>
</section>
<section id="other-key-features">
<h4>Other Key Features<a class="headerlink" href="#other-key-features" title="Permalink to this headline">¶</a></h4>
Several other key features:
<ul>
<li>Like unpacking assignments, tuple and list patterns have exactly the
same meaning and actually match arbitrary sequences. Technically,
the subject must be a sequence.
Therefore, an important exception is that patterns don’t match iterators.
Also, to prevent a common mistake, sequence patterns don’t match strings.</li>
<li>Sequence patterns support wildcards: <code class="docutils literal notranslate">[x, y, *rest]</code> and <code class="docutils literal notranslate">(x, y,
*rest)</code> work similar to wildcards in unpacking assignments. The
name after <code class="docutils literal notranslate">*</code> may also be <code class="docutils literal notranslate">_</code>, so <code class="docutils literal notranslate">(x, y, *_)</code> matches a sequence
of at least two items without binding the remaining items.</li>
<li>Mapping patterns: <code class="docutils literal notranslate">{&quot;bandwidth&quot;: b, &quot;latency&quot;: l}</code> captures the
<code class="docutils literal notranslate">&quot;bandwidth&quot;</code> and <code class="docutils literal notranslate">&quot;latency&quot;</code> values from a dict. Unlike sequence
patterns, extra keys are ignored. A wildcard <code class="docutils literal notranslate">**rest</code> is also
supported. (But <code class="docutils literal notranslate">**_</code> would be redundant, so is not allowed.)</li>
<li>Subpatterns may be captured using the <code class="docutils literal notranslate">as</code> keyword:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>case (Point(x1, y1), Point(x2, y2) as p2): ...
</pre></div>
</div>
This binds x1, y1, x2, y2 like you would expect without the <code class="docutils literal notranslate">as</code> clause,
and p2 to the entire second item of the subject.
</li>
<li>Most literals are compared by equality. However, the singletons <code class="docutils literal notranslate">True</code>,
<code class="docutils literal notranslate">False</code> and <code class="docutils literal notranslate">None</code> are compared by identity.</li>
<li>Named constants may be used in patterns. These named constants must be
dotted names to prevent the constant from being interpreted as a capture
variable:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>from enum import Enum
class Color(Enum):
 RED = 0
 GREEN = 1
 BLUE = 2

match color:
 case Color.RED:
 print(&quot;I see red!&quot;)
 case Color.GREEN:
 print(&quot;Grass is green&quot;)
 case Color.BLUE:
 print(&quot;I&#39;m feeling the blues :(&quot;)
</pre></div>
</div>
</li>
</ul>
For the full specification see <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0634">PEP 634</a>. Motivation and rationale
are in <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0635">PEP 635</a>, and a longer tutorial is in <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0636">PEP 636</a>.
</section>
</section>
<section id="optional-encodingwarning-and-encoding-locale-option">
<h3>Optional <code class="docutils literal notranslate">EncodingWarning</code> and <code class="docutils literal notranslate">encoding=&quot;locale&quot;</code> option<a class="headerlink" href="#optional-encodingwarning-and-encoding-locale-option" title="Permalink to this headline">¶</a></h3>
The default encoding of <code class="xref py py-class docutils literal notranslate">TextIOWrapper</code> and <a class="reference internal" href="../library/functions.html#open" title="open"><code class="xref py py-func docutils literal notranslate">open()</code></a> is
platform and locale dependent. Since UTF-8 is used on most Unix
platforms, omitting <code class="docutils literal notranslate">encoding</code> option when opening UTF-8 files
(e.g. JSON, YAML, TOML, Markdown) is a very common bug. For example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre># BUG: &quot;rb&quot; mode or encoding=&quot;utf-8&quot; should be used.
with open(&quot;data.json&quot;) as f:
 data = json.load(f)
</pre></div>
</div>
To find this type of bug, an optional <code class="docutils literal notranslate">EncodingWarning</code> is added.
It is emitted when <a class="reference internal" href="../library/sys.html#sys.flags" title="sys.flags"><code class="xref py py-data docutils literal notranslate">sys.flags.warn_default_encoding</code></a>
is true and locale-specific default encoding is used.
<code class="docutils literal notranslate">-X warn_default_encoding</code> option and <a class="reference internal" href="../using/cmdline.html#envvar-PYTHONWARNDEFAULTENCODING"><code class="xref std std-envvar docutils literal notranslate">PYTHONWARNDEFAULTENCODING</code></a>
are added to enable the warning.
See <a class="reference internal" href="../library/io.html#io-text-encoding">Text Encoding</a> for more information.
</section>
</section>
<section id="new-features-related-to-type-hints">
<h2>New Features Related to Type Hints<a class="headerlink" href="#new-features-related-to-type-hints" title="Permalink to this headline">¶</a></h2>
This section covers major changes affecting <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0484">PEP 484</a> type hints and
the <a class="reference internal" href="../library/typing.html#module-typing" title="typing: Support for type hints (see :pep:`484`)."><code class="xref py py-mod docutils literal notranslate">typing</code></a> module.
<section id="pep-604-new-type-union-operator">
<h3>PEP 604: New Type Union Operator<a class="headerlink" href="#pep-604-new-type-union-operator" title="Permalink to this headline">¶</a></h3>
A new type union operator was introduced which enables the syntax <code class="docutils literal notranslate">X | Y</code>.
This provides a cleaner way of expressing ‘either type X or type Y’ instead of
using <a class="reference internal" href="../library/typing.html#typing.Union" title="typing.Union"><code class="xref py py-data docutils literal notranslate">typing.Union</code></a>, especially in type hints.
In previous versions of Python, to apply a type hint for functions accepting
arguments of multiple types, <a class="reference internal" href="../library/typing.html#typing.Union" title="typing.Union"><code class="xref py py-data docutils literal notranslate">typing.Union</code></a> was used:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>def square(number: Union[int, float]) -&gt; Union[int, float]:
 return number ** 2
</pre></div>
</div>
Type hints can now be written in a more succinct manner:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>def square(number: int | float) -&gt; int | float:
 return number ** 2
</pre></div>
</div>
This new syntax is also accepted as the second argument to <a class="reference internal" href="../library/functions.html#isinstance" title="isinstance"><code class="xref py py-func docutils literal notranslate">isinstance()</code></a>
and <a class="reference internal" href="../library/functions.html#issubclass" title="issubclass"><code class="xref py py-func docutils literal notranslate">issubclass()</code></a>:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; isinstance(1, int | str)
True
</pre></div>
</div>
See <a class="reference internal" href="../library/stdtypes.html#types-union">Union Type</a> and <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0604">PEP 604</a> for more details.
(Contributed by Maggie Moss and Philippe Prados in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41428">bpo-41428</a>,
with additions by Yurii Karabas and Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=44490">bpo-44490</a>.)
</section>
<section id="pep-612-parameter-specification-variables">
<h3>PEP 612: Parameter Specification Variables<a class="headerlink" href="#pep-612-parameter-specification-variables" title="Permalink to this headline">¶</a></h3>
Two new options to improve the information provided to static type checkers for
<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0484">PEP 484</a>‘s <code class="docutils literal notranslate">Callable</code> have been added to the <a class="reference internal" href="../library/typing.html#module-typing" title="typing: Support for type hints (see :pep:`484`)."><code class="xref py py-mod docutils literal notranslate">typing</code></a> module.
The first is the parameter specification variable. They are used to forward the
parameter types of one callable to another callable – a pattern commonly
found in higher order functions and decorators. Examples of usage can be found
in <a class="reference internal" href="../library/typing.html#typing.ParamSpec" title="typing.ParamSpec"><code class="xref py py-class docutils literal notranslate">typing.ParamSpec</code></a>. Previously, there was no easy way to type annotate
dependency of parameter types in such a precise manner.
The second option is the new <code class="docutils literal notranslate">Concatenate</code> operator. It’s used in conjunction
with parameter specification variables to type annotate a higher order callable
which adds or removes parameters of another callable. Examples of usage can
be found in <a class="reference internal" href="../library/typing.html#typing.Concatenate" title="typing.Concatenate"><code class="xref py py-class docutils literal notranslate">typing.Concatenate</code></a>.
See <a class="reference internal" href="../library/typing.html#typing.Callable" title="typing.Callable"><code class="xref py py-class docutils literal notranslate">typing.Callable</code></a>, <a class="reference internal" href="../library/typing.html#typing.ParamSpec" title="typing.ParamSpec"><code class="xref py py-class docutils literal notranslate">typing.ParamSpec</code></a>,
<a class="reference internal" href="../library/typing.html#typing.Concatenate" title="typing.Concatenate"><code class="xref py py-class docutils literal notranslate">typing.Concatenate</code></a>, <a class="reference internal" href="../library/typing.html#typing.ParamSpecArgs" title="typing.ParamSpecArgs"><code class="xref py py-class docutils literal notranslate">typing.ParamSpecArgs</code></a>,
<a class="reference internal" href="../library/typing.html#typing.ParamSpecKwargs" title="typing.ParamSpecKwargs"><code class="xref py py-class docutils literal notranslate">typing.ParamSpecKwargs</code></a>, and <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0612">PEP 612</a> for more details.
(Contributed by Ken Jin in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41559">bpo-41559</a>, with minor enhancements by Jelle
Zijlstra in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43783">bpo-43783</a>. PEP written by Mark Mendoza.)
</section>
<section id="pep-613-typealias">
<h3>PEP 613: TypeAlias<a class="headerlink" href="#pep-613-typealias" title="Permalink to this headline">¶</a></h3>
<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0484">PEP 484</a> introduced the concept of type aliases, only requiring them to be
top-level unannotated assignments. This simplicity sometimes made it difficult
for type checkers to distinguish between type aliases and ordinary assignments,
especially when forward references or invalid types were involved. Compare:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>StrCache = &#39;Cache[str]&#39; # a type alias
LOG_PREFIX = &#39;LOG[DEBUG]&#39; # a module constant
</pre></div>
</div>
Now the <a class="reference internal" href="../library/typing.html#module-typing" title="typing: Support for type hints (see :pep:`484`)."><code class="xref py py-mod docutils literal notranslate">typing</code></a> module has a special value <code class="xref py py-data docutils literal notranslate">TypeAlias</code>
which lets you declare type aliases more explicitly:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>StrCache: TypeAlias = &#39;Cache[str]&#39; # a type alias
LOG_PREFIX = &#39;LOG[DEBUG]&#39; # a module constant
</pre></div>
</div>
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0613">PEP 613</a> for more details.
(Contributed by Mikhail Golubev in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41923">bpo-41923</a>.)
</section>
<section id="pep-647-user-defined-type-guards">
<h3>PEP 647: User-Defined Type Guards<a class="headerlink" href="#pep-647-user-defined-type-guards" title="Permalink to this headline">¶</a></h3>
<code class="xref py py-data docutils literal notranslate">TypeGuard</code> has been added to the <a class="reference internal" href="../library/typing.html#module-typing" title="typing: Support for type hints (see :pep:`484`)."><code class="xref py py-mod docutils literal notranslate">typing</code></a> module to annotate
type guard functions and improve information provided to static type checkers
during type narrowing. For more information, please see <code class="xref py py-data docutils literal notranslate">TypeGuard</code>‘s
documentation, and <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0647">PEP 647</a>.
(Contributed by Ken Jin and Guido van Rossum in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43766">bpo-43766</a>.
PEP written by Eric Traut.)
</section>
</section>
<section id="other-language-changes">
<h2>Other Language Changes<a class="headerlink" href="#other-language-changes" title="Permalink to this headline">¶</a></h2>
<ul class="simple">
<li>The <a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a> type has a new method <a class="reference internal" href="../library/stdtypes.html#int.bit_count" title="int.bit_count"><code class="xref py py-meth docutils literal notranslate">int.bit_count()</code></a>, returning the
number of ones in the binary expansion of a given integer, also known
as the population count. (Contributed by Niklas Fiekas in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=29882">bpo-29882</a>.)</li>
<li>The views returned by <a class="reference internal" href="../library/stdtypes.html#dict.keys" title="dict.keys"><code class="xref py py-meth docutils literal notranslate">dict.keys()</code></a>, <a class="reference internal" href="../library/stdtypes.html#dict.values" title="dict.values"><code class="xref py py-meth docutils literal notranslate">dict.values()</code></a> and
<a class="reference internal" href="../library/stdtypes.html#dict.items" title="dict.items"><code class="xref py py-meth docutils literal notranslate">dict.items()</code></a> now all have a <code class="docutils literal notranslate">mapping</code> attribute that gives a
<a class="reference internal" href="../library/types.html#types.MappingProxyType" title="types.MappingProxyType"><code class="xref py py-class docutils literal notranslate">types.MappingProxyType</code></a> object wrapping the original
dictionary. (Contributed by Dennis Sweeney in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=40890">bpo-40890</a>.)</li>
<li><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0618">PEP 618</a>: The <a class="reference internal" href="../library/functions.html#zip" title="zip"><code class="xref py py-func docutils literal notranslate">zip()</code></a> function now has an optional <code class="docutils literal notranslate">strict</code> flag, used
to require that all the iterables have an equal length.</li>
<li>Builtin and extension functions that take integer arguments no longer accept
<a class="reference internal" href="../library/decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal notranslate">Decimal</code></a>s, <a class="reference internal" href="../library/fractions.html#fractions.Fraction" title="fractions.Fraction"><code class="xref py py-class docutils literal notranslate">Fraction</code></a>s and other
objects that can be converted to integers only with a loss (e.g. that have
the <a class="reference internal" href="../reference/datamodel.html#object.__int__" title="object.__int__"><code class="xref py py-meth docutils literal notranslate">__int__()</code></a> method but do not have the
<a class="reference internal" href="../reference/datamodel.html#object.__index__" title="object.__index__"><code class="xref py py-meth docutils literal notranslate">__index__()</code></a> method).
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=37999">bpo-37999</a>.)</li>
<li>If <a class="reference internal" href="../reference/datamodel.html#object.__ipow__" title="object.__ipow__"><code class="xref py py-func docutils literal notranslate">object.__ipow__()</code></a> returns <a class="reference internal" href="../library/constants.html#NotImplemented" title="NotImplemented"><code class="xref py py-const docutils literal notranslate">NotImplemented</code></a>, the operator will
correctly fall back to <a class="reference internal" href="../reference/datamodel.html#object.__pow__" title="object.__pow__"><code class="xref py py-func docutils literal notranslate">object.__pow__()</code></a> and <a class="reference internal" href="../reference/datamodel.html#object.__rpow__" title="object.__rpow__"><code class="xref py py-func docutils literal notranslate">object.__rpow__()</code></a> as expected.
(Contributed by Alex Shkop in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=38302">bpo-38302</a>.)</li>
<li>Assignment expressions can now be used unparenthesized within set literals
and set comprehensions, as well as in sequence indexes (but not slices).</li>
<li>Functions have a new <code class="docutils literal notranslate">__builtins__</code> attribute which is used to look for
builtin symbols when a function is executed, instead of looking into
<code class="docutils literal notranslate">__globals__['__builtins__']</code>. The attribute is initialized from
<code class="docutils literal notranslate">__globals__[&quot;__builtins__&quot;]</code> if it exists, else from the current builtins.
(Contributed by Mark Shannon in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42990">bpo-42990</a>.)</li>
<li>Two new builtin functions – <a class="reference internal" href="../library/functions.html#aiter" title="aiter"><code class="xref py py-func docutils literal notranslate">aiter()</code></a> and <a class="reference internal" href="../library/functions.html#anext" title="anext"><code class="xref py py-func docutils literal notranslate">anext()</code></a> have been added
to provide asynchronous counterparts to <a class="reference internal" href="../library/functions.html#iter" title="iter"><code class="xref py py-func docutils literal notranslate">iter()</code></a> and <a class="reference internal" href="../library/functions.html#next" title="next"><code class="xref py py-func docutils literal notranslate">next()</code></a>,
respectively.
(Contributed by Joshua Bronson, Daniel Pope, and Justin Wang in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=31861">bpo-31861</a>.)</li>
<li>Static methods (<a class="reference internal" href="../library/functions.html#staticmethod" title="staticmethod"><code class="xref py py-func docutils literal notranslate">&#64;staticmethod</code></a>) and class methods
(<a class="reference internal" href="../library/functions.html#classmethod" title="classmethod"><code class="xref py py-func docutils literal notranslate">&#64;classmethod</code></a>) now inherit the method attributes
(<code class="docutils literal notranslate">__module__</code>, <code class="docutils literal notranslate">__name__</code>, <code class="docutils literal notranslate">__qualname__</code>, <code class="docutils literal notranslate">__doc__</code>,
<code class="docutils literal notranslate">__annotations__</code>) and have a new <code class="docutils literal notranslate">__wrapped__</code> attribute.
Moreover, static methods are now callable as regular functions.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43682">bpo-43682</a>.)</li>
<li>Annotations for complex targets (everything beside <code class="docutils literal notranslate">simple name</code> targets
defined by <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0526">PEP 526</a>) no longer cause any runtime effects with <code class="docutils literal notranslate">from __future__ import annotations</code>.
(Contributed by Batuhan Taskaya in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42737">bpo-42737</a>.)</li>
<li>Class and module objects now lazy-create empty annotations dicts on demand.
The annotations dicts are stored in the object’s <code class="docutils literal notranslate">__dict__</code> for
backwards compatibility. This improves the best practices for working
with <code class="docutils literal notranslate">__annotations__</code>; for more information, please see
<a class="reference internal" href="../howto/annotations.html#annotations-howto">Annotations Best Practices</a>.
(Contributed by Larry Hastings in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43901">bpo-43901</a>.)</li>
<li>Annotations consist of <code class="docutils literal notranslate">yield</code>, <code class="docutils literal notranslate">yield from</code>, <code class="docutils literal notranslate">await</code> or named expressions
are now forbidden under <code class="docutils literal notranslate">from __future__ import annotations</code> due to their side
effects.
(Contributed by Batuhan Taskaya in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42725">bpo-42725</a>.)</li>
<li>Usage of unbound variables, <code class="docutils literal notranslate">super()</code> and other expressions that might
alter the processing of symbol table as annotations are now rendered
effectless under <code class="docutils literal notranslate">from __future__ import annotations</code>.
(Contributed by Batuhan Taskaya in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42725">bpo-42725</a>.)</li>
<li>Hashes of NaN values of both <a class="reference internal" href="../library/functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate">float</code></a> type and
<a class="reference internal" href="../library/decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal notranslate">decimal.Decimal</code></a> type now depend on object identity. Formerly, they
always hashed to <code class="docutils literal notranslate">0</code> even though NaN values are not equal to one another.
This caused potentially quadratic runtime behavior due to excessive hash
collisions when creating dictionaries and sets containing multiple NaNs.
(Contributed by Raymond Hettinger in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43475">bpo-43475</a>.)</li>
<li>A <a class="reference internal" href="../library/exceptions.html#SyntaxError" title="SyntaxError"><code class="xref py py-exc docutils literal notranslate">SyntaxError</code></a> (instead of a <a class="reference internal" href="../library/exceptions.html#NameError" title="NameError"><code class="xref py py-exc docutils literal notranslate">NameError</code></a>) will be raised when deleting
the <a class="reference internal" href="../library/constants.html#debug__" title="__debug__"><code class="xref py py-const docutils literal notranslate">__debug__</code></a> constant. (Contributed by Dong-hee Na in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=45000">bpo-45000</a>.)</li>
<li><a class="reference internal" href="../library/exceptions.html#SyntaxError" title="SyntaxError"><code class="xref py py-exc docutils literal notranslate">SyntaxError</code></a> exceptions now have <code class="docutils literal notranslate">end_lineno</code> and
<code class="docutils literal notranslate">end_offset</code> attributes. They will be <code class="docutils literal notranslate">None</code> if not determined.
(Contributed by Pablo Galindo in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43914">bpo-43914</a>.)</li>
</ul>
</section>
<section id="new-modules">
<h2>New Modules<a class="headerlink" href="#new-modules" title="Permalink to this headline">¶</a></h2>
<ul class="simple">
<li>None yet.</li>
</ul>
</section>
<section id="improved-modules">
<h2>Improved Modules<a class="headerlink" href="#improved-modules" title="Permalink to this headline">¶</a></h2>
<section id="asyncio">
<h3>asyncio<a class="headerlink" href="#asyncio" title="Permalink to this headline">¶</a></h3>
Add missing <code class="xref py py-meth docutils literal notranslate">connect_accepted_socket()</code>
method.
(Contributed by Alex Grönholm in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41332">bpo-41332</a>.)
</section>
<section id="argparse">
<h3>argparse<a class="headerlink" href="#argparse" title="Permalink to this headline">¶</a></h3>
Misleading phrase “optional arguments” was replaced with “options” in argparse help. Some tests might require adaptation if they rely on exact output match.
(Contributed by Raymond Hettinger in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=9694">bpo-9694</a>.)
</section>
<section id="array">
<h3>array<a class="headerlink" href="#array" title="Permalink to this headline">¶</a></h3>
The <a class="reference internal" href="../library/array.html#array.array.index" title="array.array.index"><code class="xref py py-meth docutils literal notranslate">index()</code></a> method of <a class="reference internal" href="../library/array.html#array.array" title="array.array"><code class="xref py py-class docutils literal notranslate">array.array</code></a> now has
optional start and stop parameters.
(Contributed by Anders Lorentsen and Zackery Spytz in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=31956">bpo-31956</a>.)
</section>
<section id="asynchat-asyncore-smtpd">
<h3>asynchat, asyncore, smtpd<a class="headerlink" href="#asynchat-asyncore-smtpd" title="Permalink to this headline">¶</a></h3>
These modules have been marked as deprecated in their module documentation
since Python 3.6. An import-time <a class="reference internal" href="../library/exceptions.html#DeprecationWarning" title="DeprecationWarning"><code class="xref py py-class docutils literal notranslate">DeprecationWarning</code></a> has now been
added to all three of these modules.
</section>
<section id="base64">
<h3>base64<a class="headerlink" href="#base64" title="Permalink to this headline">¶</a></h3>
Add <a class="reference internal" href="../library/base64.html#base64.b32hexencode" title="base64.b32hexencode"><code class="xref py py-func docutils literal notranslate">base64.b32hexencode()</code></a> and <a class="reference internal" href="../library/base64.html#base64.b32hexdecode" title="base64.b32hexdecode"><code class="xref py py-func docutils literal notranslate">base64.b32hexdecode()</code></a> to support the
Base32 Encoding with Extended Hex Alphabet.
</section>
<section id="bdb">
<h3>bdb<a class="headerlink" href="#bdb" title="Permalink to this headline">¶</a></h3>
Add <code class="xref py py-meth docutils literal notranslate">clearBreakpoints()</code> to reset all set breakpoints.
(Contributed by Irit Katriel in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=24160">bpo-24160</a>.)
</section>
<section id="bisect">
<h3>bisect<a class="headerlink" href="#bisect" title="Permalink to this headline">¶</a></h3>
Added the possibility of providing a key function to the APIs in the <a class="reference internal" href="../library/bisect.html#module-bisect" title="bisect: Array bisection algorithms for binary searching."><code class="xref py py-mod docutils literal notranslate">bisect</code></a>
module. (Contributed by Raymond Hettinger in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=4356">bpo-4356</a>.)
</section>
<section id="codecs">
<h3>codecs<a class="headerlink" href="#codecs" title="Permalink to this headline">¶</a></h3>
Add a <a class="reference internal" href="../library/codecs.html#codecs.unregister" title="codecs.unregister"><code class="xref py py-func docutils literal notranslate">codecs.unregister()</code></a> function to unregister a codec search function.
(Contributed by Hai Shi in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41842">bpo-41842</a>.)
</section>
<section id="collections-abc">
<h3>collections.abc<a class="headerlink" href="#collections-abc" title="Permalink to this headline">¶</a></h3>
The <code class="docutils literal notranslate">__args__</code> of the <a class="reference internal" href="../library/stdtypes.html#types-genericalias">parameterized generic</a> for
<a class="reference internal" href="../library/collections.abc.html#collections.abc.Callable" title="collections.abc.Callable"><code class="xref py py-class docutils literal notranslate">collections.abc.Callable</code></a> are now consistent with <a class="reference internal" href="../library/typing.html#typing.Callable" title="typing.Callable"><code class="xref py py-data docutils literal notranslate">typing.Callable</code></a>.
<a class="reference internal" href="../library/collections.abc.html#collections.abc.Callable" title="collections.abc.Callable"><code class="xref py py-class docutils literal notranslate">collections.abc.Callable</code></a> generic now flattens type parameters, similar
to what <a class="reference internal" href="../library/typing.html#typing.Callable" title="typing.Callable"><code class="xref py py-data docutils literal notranslate">typing.Callable</code></a> currently does. This means that
<code class="docutils literal notranslate">collections.abc.Callable[[int, str], str]</code> will have <code class="docutils literal notranslate">__args__</code> of
<code class="docutils literal notranslate">(int, str, str)</code>; previously this was <code class="docutils literal notranslate">([int, str], str)</code>. To allow this
change, <a class="reference internal" href="../library/types.html#types.GenericAlias" title="types.GenericAlias"><code class="xref py py-class docutils literal notranslate">types.GenericAlias</code></a> can now be subclassed, and a subclass will
be returned when subscripting the <a class="reference internal" href="../library/collections.abc.html#collections.abc.Callable" title="collections.abc.Callable"><code class="xref py py-class docutils literal notranslate">collections.abc.Callable</code></a> type. Note
that a <a class="reference internal" href="../library/exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate">TypeError</code></a> may be raised for invalid forms of parameterizing
<a class="reference internal" href="../library/collections.abc.html#collections.abc.Callable" title="collections.abc.Callable"><code class="xref py py-class docutils literal notranslate">collections.abc.Callable</code></a> which may have passed silently in Python 3.9.
(Contributed by Ken Jin in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42195">bpo-42195</a>.)
</section>
<section id="contextlib">
<h3>contextlib<a class="headerlink" href="#contextlib" title="Permalink to this headline">¶</a></h3>
Add a <a class="reference internal" href="../library/contextlib.html#contextlib.aclosing" title="contextlib.aclosing"><code class="xref py py-func docutils literal notranslate">contextlib.aclosing()</code></a> context manager to safely close async generators
and objects representing asynchronously released resources.
(Contributed by Joongi Kim and John Belmonte in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41229">bpo-41229</a>.)
Add asynchronous context manager support to <a class="reference internal" href="../library/contextlib.html#contextlib.nullcontext" title="contextlib.nullcontext"><code class="xref py py-func docutils literal notranslate">contextlib.nullcontext()</code></a>.
(Contributed by Tom Gringauz in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41543">bpo-41543</a>.)
Add <code class="xref py py-class docutils literal notranslate">AsyncContextDecorator</code>, for supporting usage of async context managers
as decorators.
</section>
<section id="curses">
<h3>curses<a class="headerlink" href="#curses" title="Permalink to this headline">¶</a></h3>
The extended color functions added in ncurses 6.1 will be used transparently
by <a class="reference internal" href="../library/curses.html#curses.color_content" title="curses.color_content"><code class="xref py py-func docutils literal notranslate">curses.color_content()</code></a>, <a class="reference internal" href="../library/curses.html#curses.init_color" title="curses.init_color"><code class="xref py py-func docutils literal notranslate">curses.init_color()</code></a>,
<a class="reference internal" href="../library/curses.html#curses.init_pair" title="curses.init_pair"><code class="xref py py-func docutils literal notranslate">curses.init_pair()</code></a>, and <a class="reference internal" href="../library/curses.html#curses.pair_content" title="curses.pair_content"><code class="xref py py-func docutils literal notranslate">curses.pair_content()</code></a>. A new function,
<a class="reference internal" href="../library/curses.html#curses.has_extended_color_support" title="curses.has_extended_color_support"><code class="xref py py-func docutils literal notranslate">curses.has_extended_color_support()</code></a>, indicates whether extended color
support is provided by the underlying ncurses library.
(Contributed by Jeffrey Kintscher and Hans Petter Jansson in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=36982">bpo-36982</a>.)
The <code class="docutils literal notranslate">BUTTON5_*</code> constants are now exposed in the <a class="reference internal" href="../library/curses.html#module-curses" title="curses: An interface to the curses library, providing portable terminal handling. (Unix)"><code class="xref py py-mod docutils literal notranslate">curses</code></a> module if
they are provided by the underlying curses library.
(Contributed by Zackery Spytz in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=39273">bpo-39273</a>.)
</section>
<section id="dataclasses">
<h3>dataclasses<a class="headerlink" href="#dataclasses" title="Permalink to this headline">¶</a></h3>
<section id="slots">
<h4>__slots__<a class="headerlink" href="#slots" title="Permalink to this headline">¶</a></h4>
Added <code class="docutils literal notranslate">slots</code> parameter in <a class="reference internal" href="../library/dataclasses.html#dataclasses.dataclass" title="dataclasses.dataclass"><code class="xref py py-func docutils literal notranslate">dataclasses.dataclass()</code></a> decorator.
(Contributed by Yurii Karabas in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42269">bpo-42269</a>)
</section>
<section id="keyword-only-fields">
<h4>Keyword-only fields<a class="headerlink" href="#keyword-only-fields" title="Permalink to this headline">¶</a></h4>
dataclasses now supports fields that are keyword-only in the
generated __init__ method. There are a number of ways of specifying
keyword-only fields.
You can say that every field is keyword-only:
<div class="highlight-python notranslate"><div class="highlight"><pre>from dataclasses import dataclass

@dataclass(kw_only=True)
class Birthday:
 name: str
 birthday: datetime.date
</pre></div>
</div>
Both <code class="docutils literal notranslate">name</code> and <code class="docutils literal notranslate">birthday</code> are keyword-only parameters to the
generated __init__ method.
You can specify keyword-only on a per-field basis:
<div class="highlight-python notranslate"><div class="highlight"><pre>from dataclasses import dataclass

@dataclass
class Birthday:
 name: str
 birthday: datetime.date = field(kw_only=True)
</pre></div>
</div>
Here only <code class="docutils literal notranslate">birthday</code> is keyword-only. If you set <code class="docutils literal notranslate">kw_only</code> on
individual fields, be aware that there are rules about re-ordering
fields due to keyword-only fields needing to follow non-keyword-only
fields. See the full dataclasses documentation for details.
You can also specify that all fields following a KW_ONLY marker are
keyword-only. This will probably be the most common usage:
<div class="highlight-python notranslate"><div class="highlight"><pre>from dataclasses import dataclass, KW_ONLY

@dataclass
class Point:
 x: float
 y: float
 _: KW_ONLY
 z: float = 0.0
 t: float = 0.0
</pre></div>
</div>
Here, <code class="docutils literal notranslate">z</code> and <code class="docutils literal notranslate">t</code> are keyword-only parameters, while <code class="docutils literal notranslate">x</code> and
<code class="docutils literal notranslate">y</code> are not.
(Contributed by Eric V. Smith in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43532">bpo-43532</a>.)
</section>
</section>
<section id="distutils">
<h3>distutils<a class="headerlink" href="#distutils" title="Permalink to this headline">¶</a></h3>
The entire <code class="docutils literal notranslate">distutils</code> package is deprecated, to be removed in Python
3.12. Its functionality for specifying package builds has already been
completely replaced by third-party packages <code class="docutils literal notranslate">setuptools</code> and
<code class="docutils literal notranslate">packaging</code>, and most other commonly used APIs are available elsewhere
in the standard library (such as <a class="reference internal" href="../library/platform.html#module-platform" title="platform: Retrieves as much platform identifying data as possible."><code class="xref py py-mod docutils literal notranslate">platform</code></a>, <a class="reference internal" href="../library/shutil.html#module-shutil" title="shutil: High-level file operations, including copying."><code class="xref py py-mod docutils literal notranslate">shutil</code></a>,
<a class="reference internal" href="../library/subprocess.html#module-subprocess" title="subprocess: Subprocess management."><code class="xref py py-mod docutils literal notranslate">subprocess</code></a> or <a class="reference internal" href="../library/sysconfig.html#module-sysconfig" title="sysconfig: Python's configuration information"><code class="xref py py-mod docutils literal notranslate">sysconfig</code></a>). There are no plans to migrate
any other functionality from <code class="docutils literal notranslate">distutils</code>, and applications that are
using other functions should plan to make private copies of the code.
Refer to <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0632">PEP 632</a> for discussion.
The <code class="docutils literal notranslate">bdist_wininst</code> command deprecated in Python 3.8 has been removed.
The <code class="docutils literal notranslate">bdist_wheel</code> command is now recommended to distribute binary packages
on Windows.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42802">bpo-42802</a>.)
</section>
<section id="doctest">
<h3>doctest<a class="headerlink" href="#doctest" title="Permalink to this headline">¶</a></h3>
When a module does not define <code class="docutils literal notranslate">__loader__</code>, fall back to <code class="docutils literal notranslate">__spec__.loader</code>.
(Contributed by Brett Cannon in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42133">bpo-42133</a>.)
</section>
<section id="encodings">
<h3>encodings<a class="headerlink" href="#encodings" title="Permalink to this headline">¶</a></h3>
<code class="xref py py-func docutils literal notranslate">encodings.normalize_encoding()</code> now ignores non-ASCII characters.
(Contributed by Hai Shi in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=39337">bpo-39337</a>.)
</section>
<section id="fileinput">
<h3>fileinput<a class="headerlink" href="#fileinput" title="Permalink to this headline">¶</a></h3>
Add encoding and errors parameters in <a class="reference internal" href="../library/fileinput.html#fileinput.input" title="fileinput.input"><code class="xref py py-func docutils literal notranslate">fileinput.input()</code></a> and
<a class="reference internal" href="../library/fileinput.html#fileinput.FileInput" title="fileinput.FileInput"><code class="xref py py-class docutils literal notranslate">fileinput.FileInput</code></a>.
(Contributed by Inada Naoki in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43712">bpo-43712</a>.)
<a class="reference internal" href="../library/fileinput.html#fileinput.hook_compressed" title="fileinput.hook_compressed"><code class="xref py py-func docutils literal notranslate">fileinput.hook_compressed()</code></a> now returns <code class="xref py py-class docutils literal notranslate">TextIOWrapper</code> object
when mode is “r” and file is compressed, like uncompressed files.
(Contributed by Inada Naoki in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5758">bpo-5758</a>.)
</section>
<section id="faulthandler">
<h3>faulthandler<a class="headerlink" href="#faulthandler" title="Permalink to this headline">¶</a></h3>
The <a class="reference internal" href="../library/faulthandler.html#module-faulthandler" title="faulthandler: Dump the Python traceback."><code class="xref py py-mod docutils literal notranslate">faulthandler</code></a> module now detects if a fatal error occurs during a
garbage collector collection.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=44466">bpo-44466</a>.)
</section>
<section id="gc">
<h3>gc<a class="headerlink" href="#gc" title="Permalink to this headline">¶</a></h3>
Add audit hooks for <a class="reference internal" href="../library/gc.html#gc.get_objects" title="gc.get_objects"><code class="xref py py-func docutils literal notranslate">gc.get_objects()</code></a>, <a class="reference internal" href="../library/gc.html#gc.get_referrers" title="gc.get_referrers"><code class="xref py py-func docutils literal notranslate">gc.get_referrers()</code></a> and
<a class="reference internal" href="../library/gc.html#gc.get_referents" title="gc.get_referents"><code class="xref py py-func docutils literal notranslate">gc.get_referents()</code></a>. (Contributed by Pablo Galindo in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43439">bpo-43439</a>.)
</section>
<section id="glob">
<h3>glob<a class="headerlink" href="#glob" title="Permalink to this headline">¶</a></h3>
Add the root_dir and dir_fd parameters in <a class="reference internal" href="../library/glob.html#glob.glob" title="glob.glob"><code class="xref py py-func docutils literal notranslate">glob()</code></a> and
<a class="reference internal" href="../library/glob.html#glob.iglob" title="glob.iglob"><code class="xref py py-func docutils literal notranslate">iglob()</code></a> which allow to specify the root directory for searching.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=38144">bpo-38144</a>.)
</section>
<section id="hashlib">
<h3>hashlib<a class="headerlink" href="#hashlib" title="Permalink to this headline">¶</a></h3>
The hashlib module requires OpenSSL 1.1.1 or newer.
(Contributed by Christian Heimes in <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0644">PEP 644</a> and <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43669">bpo-43669</a>.)
The hashlib module has preliminary support for OpenSSL 3.0.0.
(Contributed by Christian Heimes in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=38820">bpo-38820</a> and other issues.)
The pure-Python fallback of <a class="reference internal" href="../library/hashlib.html#hashlib.pbkdf2_hmac" title="hashlib.pbkdf2_hmac"><code class="xref py py-func docutils literal notranslate">pbkdf2_hmac()</code></a> is deprecated. In
the future PBKDF2-HMAC will only be available when Python has been built with
OpenSSL support.
(Contributed by Christian Heimes in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43880">bpo-43880</a>.)
</section>
<section id="hmac">
<h3>hmac<a class="headerlink" href="#hmac" title="Permalink to this headline">¶</a></h3>
The hmac module now uses OpenSSL’s HMAC implementation internally.
(Contributed by Christian Heimes in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=40645">bpo-40645</a>.)
</section>
<section id="idle-and-idlelib">
<h3>IDLE and idlelib<a class="headerlink" href="#idle-and-idlelib" title="Permalink to this headline">¶</a></h3>
Make IDLE invoke <a class="reference internal" href="../library/sys.html#sys.excepthook" title="sys.excepthook"><code class="xref py py-func docutils literal notranslate">sys.excepthook()</code></a> (when started without ‘-n’).
User hooks were previously ignored. (Contributed by Ken Hilton in
<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43008">bpo-43008</a>.)
Rearrange the settings dialog. Split the General tab into Windows
and Shell/Ed tabs. Move help sources, which extend the Help menu, to the
Extensions tab. Make space for new options and shorten the dialog. The
latter makes the dialog better fit small screens. (Contributed by Terry Jan
Reedy in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=40468">bpo-40468</a>.) Move the indent space setting from the Font tab to
the new Windows tab. (Contributed by Mark Roseman and Terry Jan Reedy in
<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=33962">bpo-33962</a>.)
The changes above were backported to a 3.9 maintenance release.
Add a Shell sidebar. Move the primary prompt (‘&gt;&gt;&gt;’) to the sidebar.
Add secondary prompts (’…’) to the sidebar. Left click and optional
drag selects one or more lines of text, as with the editor
line number sidebar. Right click after selecting text lines displays
a context menu with ‘copy with prompts’. This zips together prompts
from the sidebar with lines from the selected text. This option also
appears on the context menu for the text. (Contributed by Tal Einat
in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=37903">bpo-37903</a>.)
Use spaces instead of tabs to indent interactive code. This makes
interactive code entries ‘look right’. Making this feasible was a
major motivation for adding the shell sidebar. (Contributed by
Terry Jan Reedy in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=37892">bpo-37892</a>.)
Highlight the new <a class="reference internal" href="../reference/lexical_analysis.html#soft-keywords">soft keywords</a> <a class="reference internal" href="../reference/compound_stmts.html#match"><code class="xref std std-keyword docutils literal notranslate">match</code></a>,
<a class="reference internal" href="../reference/compound_stmts.html#match"><code class="xref std std-keyword docutils literal notranslate">case</code></a>, and <a class="reference internal" href="../reference/compound_stmts.html#wildcard-patterns"><code class="xref std std-keyword docutils literal notranslate">_</code></a> in
pattern-matching statements. However, this highlighting is not perfect
and will be incorrect in some rare cases, including some <code class="docutils literal notranslate">_</code>-s in
<code class="docutils literal notranslate">case</code> patterns. (Contributed by Tal Einat in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=44010">bpo-44010</a>.)
New in 3.10 maintenance releases.
Apply syntax highlighting to <code class="docutils literal notranslate">.pyi</code> files. (Contributed by Alex
Waygood and Terry Jan Reedy in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=45447">bpo-45447</a>.)
Include prompts when saving Shell with inputs and outputs.
(Contributed by Terry Jan Reedy in <a class="reference external" href="https://github.com/python/cpython/issues/95191">gh-95191</a>.)
</section>
<section id="importlib-metadata">
<h3>importlib.metadata<a class="headerlink" href="#importlib-metadata" title="Permalink to this headline">¶</a></h3>
Feature parity with <code class="docutils literal notranslate">importlib_metadata</code> 4.6
(<a class="reference external" href="https://importlib-metadata.readthedocs.io/en/latest/history.html">history</a>).
<a class="reference internal" href="../library/importlib.metadata.html#entry-points">importlib.metadata entry points</a>
now provide a nicer experience
for selecting entry points by group and name through a new
<code class="xref py py-class docutils literal notranslate">importlib.metadata.EntryPoints</code> class. See the Compatibility
Note in the docs for more info on the deprecation and usage.
Added <code class="xref py py-func docutils literal notranslate">importlib.metadata.packages_distributions()</code> for resolving
top-level Python modules and packages to their
<code class="xref py py-class docutils literal notranslate">importlib.metadata.Distribution</code>.
</section>
<section id="inspect">
<h3>inspect<a class="headerlink" href="#inspect" title="Permalink to this headline">¶</a></h3>
When a module does not define <code class="docutils literal notranslate">__loader__</code>, fall back to <code class="docutils literal notranslate">__spec__.loader</code>.
(Contributed by Brett Cannon in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42133">bpo-42133</a>.)
Add <a class="reference internal" href="../library/inspect.html#inspect.get_annotations" title="inspect.get_annotations"><code class="xref py py-func docutils literal notranslate">inspect.get_annotations()</code></a>, which safely computes the annotations
defined on an object. It works around the quirks of accessing the annotations
on various types of objects, and makes very few assumptions about the object
it examines. <a class="reference internal" href="../library/inspect.html#inspect.get_annotations" title="inspect.get_annotations"><code class="xref py py-func docutils literal notranslate">inspect.get_annotations()</code></a> can also correctly un-stringize
stringized annotations. <a class="reference internal" href="../library/inspect.html#inspect.get_annotations" title="inspect.get_annotations"><code class="xref py py-func docutils literal notranslate">inspect.get_annotations()</code></a> is now considered
best practice for accessing the annotations dict defined on any Python object;
for more information on best practices for working with annotations, please see
<a class="reference internal" href="../howto/annotations.html#annotations-howto">Annotations Best Practices</a>.
Relatedly, <a class="reference internal" href="../library/inspect.html#inspect.signature" title="inspect.signature"><code class="xref py py-func docutils literal notranslate">inspect.signature()</code></a>,
<a class="reference internal" href="../library/inspect.html#inspect.Signature.from_callable" title="inspect.Signature.from_callable"><code class="xref py py-func docutils literal notranslate">inspect.Signature.from_callable()</code></a>, and <code class="xref py py-func docutils literal notranslate">inspect.Signature.from_function()</code>
now call <a class="reference internal" href="../library/inspect.html#inspect.get_annotations" title="inspect.get_annotations"><code class="xref py py-func docutils literal notranslate">inspect.get_annotations()</code></a> to retrieve annotations. This means
<a class="reference internal" href="../library/inspect.html#inspect.signature" title="inspect.signature"><code class="xref py py-func docutils literal notranslate">inspect.signature()</code></a> and <a class="reference internal" href="../library/inspect.html#inspect.Signature.from_callable" title="inspect.Signature.from_callable"><code class="xref py py-func docutils literal notranslate">inspect.Signature.from_callable()</code></a> can
also now un-stringize stringized annotations.
(Contributed by Larry Hastings in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43817">bpo-43817</a>.)
</section>
<section id="itertools">
<h3>itertools<a class="headerlink" href="#itertools" title="Permalink to this headline">¶</a></h3>
Add <a class="reference internal" href="../library/itertools.html#itertools.pairwise" title="itertools.pairwise"><code class="xref py py-func docutils literal notranslate">itertools.pairwise()</code></a>.
(Contributed by Raymond Hettinger in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=38200">bpo-38200</a>.)
</section>
<section id="linecache">
<h3>linecache<a class="headerlink" href="#linecache" title="Permalink to this headline">¶</a></h3>
When a module does not define <code class="docutils literal notranslate">__loader__</code>, fall back to <code class="docutils literal notranslate">__spec__.loader</code>.
(Contributed by Brett Cannon in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42133">bpo-42133</a>.)
</section>
<section id="os">
<h3>os<a class="headerlink" href="#os" title="Permalink to this headline">¶</a></h3>
Add <a class="reference internal" href="../library/os.html#os.cpu_count" title="os.cpu_count"><code class="xref py py-func docutils literal notranslate">os.cpu_count()</code></a> support for VxWorks RTOS.
(Contributed by Peixing Xin in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41440">bpo-41440</a>.)
Add a new function <a class="reference internal" href="../library/os.html#os.eventfd" title="os.eventfd"><code class="xref py py-func docutils literal notranslate">os.eventfd()</code></a> and related helpers to wrap the
<code class="docutils literal notranslate">eventfd2</code> syscall on Linux.
(Contributed by Christian Heimes in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41001">bpo-41001</a>.)
Add <a class="reference internal" href="../library/os.html#os.splice" title="os.splice"><code class="xref py py-func docutils literal notranslate">os.splice()</code></a> that allows to move data between two file
descriptors without copying between kernel address space and user
address space, where one of the file descriptors must refer to a
pipe. (Contributed by Pablo Galindo in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41625">bpo-41625</a>.)
Add <a class="reference internal" href="../library/os.html#os.O_EVTONLY" title="os.O_EVTONLY"><code class="xref py py-data docutils literal notranslate">O_EVTONLY</code></a>, <a class="reference internal" href="../library/os.html#os.O_FSYNC" title="os.O_FSYNC"><code class="xref py py-data docutils literal notranslate">O_FSYNC</code></a>, <a class="reference internal" href="../library/os.html#os.O_SYMLINK" title="os.O_SYMLINK"><code class="xref py py-data docutils literal notranslate">O_SYMLINK</code></a>
and <a class="reference internal" href="../library/os.html#os.O_NOFOLLOW_ANY" title="os.O_NOFOLLOW_ANY"><code class="xref py py-data docutils literal notranslate">O_NOFOLLOW_ANY</code></a> for macOS.
(Contributed by Dong-hee Na in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43106">bpo-43106</a>.)
</section>
<section id="os-path">
<h3>os.path<a class="headerlink" href="#os-path" title="Permalink to this headline">¶</a></h3>
<a class="reference internal" href="../library/os.path.html#os.path.realpath" title="os.path.realpath"><code class="xref py py-func docutils literal notranslate">os.path.realpath()</code></a> now accepts a strict keyword-only argument. When set
to <code class="docutils literal notranslate">True</code>, <a class="reference internal" href="../library/exceptions.html#OSError" title="OSError"><code class="xref py py-exc docutils literal notranslate">OSError</code></a> is raised if a path doesn’t exist or a symlink loop
is encountered.
(Contributed by Barney Gale in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43757">bpo-43757</a>.)
</section>
<section id="pathlib">
<h3>pathlib<a class="headerlink" href="#pathlib" title="Permalink to this headline">¶</a></h3>
Add slice support to <a class="reference internal" href="../library/pathlib.html#pathlib.PurePath.parents" title="pathlib.PurePath.parents"><code class="xref py py-attr docutils literal notranslate">PurePath.parents</code></a>.
(Contributed by Joshua Cannon in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=35498">bpo-35498</a>.)
Add negative indexing support to <a class="reference internal" href="../library/pathlib.html#pathlib.PurePath.parents" title="pathlib.PurePath.parents"><code class="xref py py-attr docutils literal notranslate">PurePath.parents</code></a>.
(Contributed by Yaroslav Pankovych in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=21041">bpo-21041</a>.)
Add <a class="reference internal" href="../library/pathlib.html#pathlib.Path.hardlink_to" title="pathlib.Path.hardlink_to"><code class="xref py py-meth docutils literal notranslate">Path.hardlink_to</code></a> method that
supersedes <a class="reference internal" href="../library/pathlib.html#pathlib.Path.link_to" title="pathlib.Path.link_to"><code class="xref py py-meth docutils literal notranslate">link_to()</code></a>. The new method has the same argument
order as <a class="reference internal" href="../library/pathlib.html#pathlib.Path.symlink_to" title="pathlib.Path.symlink_to"><code class="xref py py-meth docutils literal notranslate">symlink_to()</code></a>.
(Contributed by Barney Gale in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=39950">bpo-39950</a>.)
<a class="reference internal" href="../library/pathlib.html#pathlib.Path.stat" title="pathlib.Path.stat"><code class="xref py py-meth docutils literal notranslate">pathlib.Path.stat()</code></a> and <a class="reference internal" href="../library/pathlib.html#pathlib.Path.chmod" title="pathlib.Path.chmod"><code class="xref py py-meth docutils literal notranslate">chmod()</code></a> now accept a
follow_symlinks keyword-only argument for consistency with corresponding
functions in the <a class="reference internal" href="../library/os.html#module-os" title="os: Miscellaneous operating system interfaces."><code class="xref py py-mod docutils literal notranslate">os</code></a> module.
(Contributed by Barney Gale in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=39906">bpo-39906</a>.)
</section>
<section id="platform">
<h3>platform<a class="headerlink" href="#platform" title="Permalink to this headline">¶</a></h3>
Add <a class="reference internal" href="../library/platform.html#platform.freedesktop_os_release" title="platform.freedesktop_os_release"><code class="xref py py-func docutils literal notranslate">platform.freedesktop_os_release()</code></a> to retrieve operation system
identification from <a class="reference external" href="https://www.freedesktop.org/software/systemd/man/os-release.html">freedesktop.org os-release</a> standard file.
(Contributed by Christian Heimes in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=28468">bpo-28468</a>.)
</section>
<section id="pprint">
<h3>pprint<a class="headerlink" href="#pprint" title="Permalink to this headline">¶</a></h3>
<a class="reference internal" href="../library/pprint.html#pprint.pprint" title="pprint.pprint"><code class="xref py py-func docutils literal notranslate">pprint.pprint()</code></a> now accepts a new <code class="docutils literal notranslate">underscore_numbers</code> keyword argument.
(Contributed by sblondon in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42914">bpo-42914</a>.)
<a class="reference internal" href="../library/pprint.html#module-pprint" title="pprint: Data pretty printer."><code class="xref py py-mod docutils literal notranslate">pprint</code></a> can now pretty-print <a class="reference internal" href="../library/dataclasses.html#dataclasses.dataclass" title="dataclasses.dataclass"><code class="xref py py-class docutils literal notranslate">dataclasses.dataclass</code></a> instances.
(Contributed by Lewis Gaul in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43080">bpo-43080</a>.)
</section>
<section id="py-compile">
<h3>py_compile<a class="headerlink" href="#py-compile" title="Permalink to this headline">¶</a></h3>
Add <code class="docutils literal notranslate">--quiet</code> option to command-line interface of <a class="reference internal" href="../library/py_compile.html#module-py_compile" title="py_compile: Generate byte-code files from Python source files."><code class="xref py py-mod docutils literal notranslate">py_compile</code></a>.
(Contributed by Gregory Schevchenko in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=38731">bpo-38731</a>.)
</section>
<section id="pyclbr">
<h3>pyclbr<a class="headerlink" href="#pyclbr" title="Permalink to this headline">¶</a></h3>
Add an <code class="docutils literal notranslate">end_lineno</code> attribute to the <code class="docutils literal notranslate">Function</code> and <code class="docutils literal notranslate">Class</code>
objects in the tree returned by <code class="xref py py-func docutils literal notranslate">pyclbr.readline()</code> and
<code class="xref py py-func docutils literal notranslate">pyclbr.readline_ex()</code>. It matches the existing (start) <code class="docutils literal notranslate">lineno</code>.
(Contributed by Aviral Srivastava in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=38307">bpo-38307</a>.)
</section>
<section id="shelve">
<h3>shelve<a class="headerlink" href="#shelve" title="Permalink to this headline">¶</a></h3>
The <a class="reference internal" href="../library/shelve.html#module-shelve" title="shelve: Python object persistence."><code class="xref py py-mod docutils literal notranslate">shelve</code></a> module now uses <a class="reference internal" href="../library/pickle.html#pickle.DEFAULT_PROTOCOL" title="pickle.DEFAULT_PROTOCOL"><code class="xref py py-data docutils literal notranslate">pickle.DEFAULT_PROTOCOL</code></a> by default
instead of <a class="reference internal" href="../library/pickle.html#module-pickle" title="pickle: Convert Python objects to streams of bytes and back."><code class="xref py py-mod docutils literal notranslate">pickle</code></a> protocol <code class="docutils literal notranslate">3</code> when creating shelves.
(Contributed by Zackery Spytz in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=34204">bpo-34204</a>.)
</section>
<section id="statistics">
<h3>statistics<a class="headerlink" href="#statistics" title="Permalink to this headline">¶</a></h3>
Add <a class="reference internal" href="../library/statistics.html#statistics.covariance" title="statistics.covariance"><code class="xref py py-func docutils literal notranslate">covariance()</code></a>, Pearson’s
<a class="reference internal" href="../library/statistics.html#statistics.correlation" title="statistics.correlation"><code class="xref py py-func docutils literal notranslate">correlation()</code></a>, and simple
<a class="reference internal" href="../library/statistics.html#statistics.linear_regression" title="statistics.linear_regression"><code class="xref py py-func docutils literal notranslate">linear_regression()</code></a> functions.
(Contributed by Tymoteusz Wołodźko in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=38490">bpo-38490</a>.)
</section>
<section id="site">
<h3>site<a class="headerlink" href="#site" title="Permalink to this headline">¶</a></h3>
When a module does not define <code class="docutils literal notranslate">__loader__</code>, fall back to <code class="docutils literal notranslate">__spec__.loader</code>.
(Contributed by Brett Cannon in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42133">bpo-42133</a>.)
</section>
<section id="socket">
<h3>socket<a class="headerlink" href="#socket" title="Permalink to this headline">¶</a></h3>
The exception <a class="reference internal" href="../library/socket.html#socket.timeout" title="socket.timeout"><code class="xref py py-exc docutils literal notranslate">socket.timeout</code></a> is now an alias of <a class="reference internal" href="../library/exceptions.html#TimeoutError" title="TimeoutError"><code class="xref py py-exc docutils literal notranslate">TimeoutError</code></a>.
(Contributed by Christian Heimes in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42413">bpo-42413</a>.)
Add option to create MPTCP sockets with <code class="docutils literal notranslate">IPPROTO_MPTCP</code>
(Contributed by Rui Cunha in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43571">bpo-43571</a>.)
Add <code class="docutils literal notranslate">IP_RECVTOS</code> option to receive the type of service (ToS) or DSCP/ECN fields
(Contributed by Georg Sauthoff in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=44077">bpo-44077</a>.)
</section>
<section id="ssl">
<h3>ssl<a class="headerlink" href="#ssl" title="Permalink to this headline">¶</a></h3>
The ssl module requires OpenSSL 1.1.1 or newer.
(Contributed by Christian Heimes in <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0644">PEP 644</a> and <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43669">bpo-43669</a>.)
The ssl module has preliminary support for OpenSSL 3.0.0 and new option
<a class="reference internal" href="../library/ssl.html#ssl.OP_IGNORE_UNEXPECTED_EOF" title="ssl.OP_IGNORE_UNEXPECTED_EOF"><code class="xref py py-data docutils literal notranslate">OP_IGNORE_UNEXPECTED_EOF</code></a>.
(Contributed by Christian Heimes in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=38820">bpo-38820</a>, <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43794">bpo-43794</a>,
<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43788">bpo-43788</a>, <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43791">bpo-43791</a>, <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43799">bpo-43799</a>, <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43920">bpo-43920</a>,
<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43789">bpo-43789</a>, and <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43811">bpo-43811</a>.)
Deprecated function and use of deprecated constants now result in
a <a class="reference internal" href="../library/exceptions.html#DeprecationWarning" title="DeprecationWarning"><code class="xref py py-exc docutils literal notranslate">DeprecationWarning</code></a>. <a class="reference internal" href="../library/ssl.html#ssl.SSLContext.options" title="ssl.SSLContext.options"><code class="xref py py-attr docutils literal notranslate">ssl.SSLContext.options</code></a> has
<a class="reference internal" href="../library/ssl.html#ssl.OP_NO_SSLv2" title="ssl.OP_NO_SSLv2"><code class="xref py py-data docutils literal notranslate">OP_NO_SSLv2</code></a> and <a class="reference internal" href="../library/ssl.html#ssl.OP_NO_SSLv3" title="ssl.OP_NO_SSLv3"><code class="xref py py-data docutils literal notranslate">OP_NO_SSLv3</code></a> set by default and
therefore cannot warn about setting the flag again. The
<a class="reference internal" href="#whatsnew310-deprecated">deprecation section</a> has a list of deprecated
features.
(Contributed by Christian Heimes in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43880">bpo-43880</a>.)
The ssl module now has more secure default settings. Ciphers without forward
secrecy or SHA-1 MAC are disabled by default. Security level 2 prohibits
weak RSA, DH, and ECC keys with less than 112 bits of security.
<a class="reference internal" href="../library/ssl.html#ssl.SSLContext" title="ssl.SSLContext"><code class="xref py py-class docutils literal notranslate">SSLContext</code></a> defaults to minimum protocol version TLS 1.2.
Settings are based on Hynek Schlawack’s research.
(Contributed by Christian Heimes in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43998">bpo-43998</a>.)
The deprecated protocols SSL 3.0, TLS 1.0, and TLS 1.1 are no longer
officially supported. Python does not block them actively. However
OpenSSL build options, distro configurations, vendor patches, and cipher
suites may prevent a successful handshake.
Add a timeout parameter to the <a class="reference internal" href="../library/ssl.html#ssl.get_server_certificate" title="ssl.get_server_certificate"><code class="xref py py-func docutils literal notranslate">ssl.get_server_certificate()</code></a> function.
(Contributed by Zackery Spytz in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=31870">bpo-31870</a>.)
The ssl module uses heap-types and multi-phase initialization.
(Contributed by Christian Heimes in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42333">bpo-42333</a>.)
A new verify flag <a class="reference internal" href="../library/ssl.html#ssl.VERIFY_X509_PARTIAL_CHAIN" title="ssl.VERIFY_X509_PARTIAL_CHAIN"><code class="xref py py-data docutils literal notranslate">VERIFY_X509_PARTIAL_CHAIN</code></a> has been added.
(Contributed by l0x in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=40849">bpo-40849</a>.)
</section>
<section id="sqlite3">
<h3>sqlite3<a class="headerlink" href="#sqlite3" title="Permalink to this headline">¶</a></h3>
Add audit events for <code class="xref py py-func docutils literal notranslate">connect/handle()</code>,
<a class="reference internal" href="../library/sqlite3.html#sqlite3.Connection.enable_load_extension" title="sqlite3.Connection.enable_load_extension"><code class="xref py py-meth docutils literal notranslate">enable_load_extension()</code></a>, and
<a class="reference internal" href="../library/sqlite3.html#sqlite3.Connection.load_extension" title="sqlite3.Connection.load_extension"><code class="xref py py-meth docutils literal notranslate">load_extension()</code></a>.
(Contributed by Erlend E. Aasland in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43762">bpo-43762</a>.)
</section>
<section id="sys">
<h3>sys<a class="headerlink" href="#sys" title="Permalink to this headline">¶</a></h3>
Add <a class="reference internal" href="../library/sys.html#sys.orig_argv" title="sys.orig_argv"><code class="xref py py-data docutils literal notranslate">sys.orig_argv</code></a> attribute: the list of the original command line
arguments passed to the Python executable.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=23427">bpo-23427</a>.)
Add <a class="reference internal" href="../library/sys.html#sys.stdlib_module_names" title="sys.stdlib_module_names"><code class="xref py py-data docutils literal notranslate">sys.stdlib_module_names</code></a>, containing the list of the standard library
module names.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42955">bpo-42955</a>.)
</section>
<section id="thread">
<h3>_thread<a class="headerlink" href="#thread" title="Permalink to this headline">¶</a></h3>
<a class="reference internal" href="../library/_thread.html#thread.interrupt_main" title="_thread.interrupt_main"><code class="xref py py-func docutils literal notranslate">_thread.interrupt_main()</code></a> now takes an optional signal number to
simulate (the default is still <a class="reference internal" href="../library/signal.html#signal.SIGINT" title="signal.SIGINT"><code class="xref py py-data docutils literal notranslate">signal.SIGINT</code></a>).
(Contributed by Antoine Pitrou in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43356">bpo-43356</a>.)
</section>
<section id="threading">
<h3>threading<a class="headerlink" href="#threading" title="Permalink to this headline">¶</a></h3>
Add <a class="reference internal" href="../library/threading.html#threading.gettrace" title="threading.gettrace"><code class="xref py py-func docutils literal notranslate">threading.gettrace()</code></a> and <a class="reference internal" href="../library/threading.html#threading.getprofile" title="threading.getprofile"><code class="xref py py-func docutils literal notranslate">threading.getprofile()</code></a> to
retrieve the functions set by <a class="reference internal" href="../library/threading.html#threading.settrace" title="threading.settrace"><code class="xref py py-func docutils literal notranslate">threading.settrace()</code></a> and
<a class="reference internal" href="../library/threading.html#threading.setprofile" title="threading.setprofile"><code class="xref py py-func docutils literal notranslate">threading.setprofile()</code></a> respectively.
(Contributed by Mario Corchero in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42251">bpo-42251</a>.)
Add <a class="reference internal" href="../library/threading.html#threading.__excepthook__" title="threading.__excepthook__"><code class="xref py py-data docutils literal notranslate">threading.__excepthook__</code></a> to allow retrieving the original value
of <a class="reference internal" href="../library/threading.html#threading.excepthook" title="threading.excepthook"><code class="xref py py-func docutils literal notranslate">threading.excepthook()</code></a> in case it is set to a broken or a different
value.
(Contributed by Mario Corchero in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42308">bpo-42308</a>.)
</section>
<section id="traceback">
<h3>traceback<a class="headerlink" href="#traceback" title="Permalink to this headline">¶</a></h3>
The <a class="reference internal" href="../library/traceback.html#traceback.format_exception" title="traceback.format_exception"><code class="xref py py-func docutils literal notranslate">format_exception()</code></a>,
<a class="reference internal" href="../library/traceback.html#traceback.format_exception_only" title="traceback.format_exception_only"><code class="xref py py-func docutils literal notranslate">format_exception_only()</code></a>, and
<a class="reference internal" href="../library/traceback.html#traceback.print_exception" title="traceback.print_exception"><code class="xref py py-func docutils literal notranslate">print_exception()</code></a> functions can now take an exception object
as a positional-only argument.
(Contributed by Zackery Spytz and Matthias Bussonnier in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=26389">bpo-26389</a>.)
</section>
<section id="types">
<h3>types<a class="headerlink" href="#types" title="Permalink to this headline">¶</a></h3>
Reintroduce the <a class="reference internal" href="../library/types.html#types.EllipsisType" title="types.EllipsisType"><code class="xref py py-data docutils literal notranslate">types.EllipsisType</code></a>, <a class="reference internal" href="../library/types.html#types.NoneType" title="types.NoneType"><code class="xref py py-data docutils literal notranslate">types.NoneType</code></a>
and <a class="reference internal" href="../library/types.html#types.NotImplementedType" title="types.NotImplementedType"><code class="xref py py-data docutils literal notranslate">types.NotImplementedType</code></a> classes, providing a new set
of types readily interpretable by type checkers.
(Contributed by Bas van Beek in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41810">bpo-41810</a>.)
</section>
<section id="typing">
<h3>typing<a class="headerlink" href="#typing" title="Permalink to this headline">¶</a></h3>
For major changes, see <a class="reference internal" href="#new-feat-related-type-hints">New Features Related to Type Hints</a>.
The behavior of <a class="reference internal" href="../library/typing.html#typing.Literal" title="typing.Literal"><code class="xref py py-class docutils literal notranslate">typing.Literal</code></a> was changed to conform with <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0586">PEP 586</a>
and to match the behavior of static type checkers specified in the PEP.
<ol class="arabic">
<li><code class="docutils literal notranslate">Literal</code> now de-duplicates parameters.</li>
<li>Equality comparisons between <code class="docutils literal notranslate">Literal</code> objects are now order independent.</li>
<li><code class="docutils literal notranslate">Literal</code> comparisons now respect types. For example,
<code class="docutils literal notranslate">Literal[0] == Literal[False]</code> previously evaluated to <code class="docutils literal notranslate">True</code>. It is
now <code class="docutils literal notranslate">False</code>. To support this change, the internally used type cache now
supports differentiating types.</li>
<li><code class="docutils literal notranslate">Literal</code> objects will now raise a <a class="reference internal" href="../library/exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate">TypeError</code></a> exception during
equality comparisons if any of their parameters are not <a class="reference internal" href="../glossary.html#term-hashable">hashable</a>.
Note that declaring <code class="docutils literal notranslate">Literal</code> with unhashable parameters will not throw
an error:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; from typing import Literal
&gt;&gt;&gt; Literal[{0}]
&gt;&gt;&gt; Literal[{0}] == Literal[{False}]
Traceback (most recent call last):
 File &quot;&lt;stdin&gt;&quot;, line 1, in &lt;module&gt;
TypeError: unhashable type: &#39;set&#39;
</pre></div>
</div>
</li>
</ol>
(Contributed by Yurii Karabas in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42345">bpo-42345</a>.)
Add new function <a class="reference internal" href="../library/typing.html#typing.is_typeddict" title="typing.is_typeddict"><code class="xref py py-func docutils literal notranslate">typing.is_typeddict()</code></a> to introspect if an annotation
is a <a class="reference internal" href="../library/typing.html#typing.TypedDict" title="typing.TypedDict"><code class="xref py py-class docutils literal notranslate">typing.TypedDict</code></a>.
(Contributed by Patrick Reader in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41792">bpo-41792</a>.)
Subclasses of <code class="docutils literal notranslate">typing.Protocol</code> which only have data variables declared
will now raise a <code class="docutils literal notranslate">TypeError</code> when checked with <code class="docutils literal notranslate">isinstance</code> unless they
are decorated with <code class="xref py py-func docutils literal notranslate">runtime_checkable()</code>. Previously, these checks
passed silently. Users should decorate their
subclasses with the <code class="xref py py-func docutils literal notranslate">runtime_checkable()</code> decorator
if they want runtime protocols.
(Contributed by Yurii Karabas in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=38908">bpo-38908</a>.)
Importing from the <code class="docutils literal notranslate">typing.io</code> and <code class="docutils literal notranslate">typing.re</code> submodules will now emit
<a class="reference internal" href="../library/exceptions.html#DeprecationWarning" title="DeprecationWarning"><code class="xref py py-exc docutils literal notranslate">DeprecationWarning</code></a>. These submodules have been deprecated since
Python 3.8 and will be removed in a future version of Python. Anything
belonging to those submodules should be imported directly from
<a class="reference internal" href="../library/typing.html#module-typing" title="typing: Support for type hints (see :pep:`484`)."><code class="xref py py-mod docutils literal notranslate">typing</code></a> instead.
(Contributed by Sebastian Rittau in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=38291">bpo-38291</a>.)
</section>
<section id="unittest">
<h3>unittest<a class="headerlink" href="#unittest" title="Permalink to this headline">¶</a></h3>
Add new method <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertNoLogs" title="unittest.TestCase.assertNoLogs"><code class="xref py py-meth docutils literal notranslate">assertNoLogs()</code></a> to complement the
existing <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertLogs" title="unittest.TestCase.assertLogs"><code class="xref py py-meth docutils literal notranslate">assertLogs()</code></a>. (Contributed by Kit Yan Choi
in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=39385">bpo-39385</a>.)
</section>
<section id="urllib-parse">
<h3>urllib.parse<a class="headerlink" href="#urllib-parse" title="Permalink to this headline">¶</a></h3>
Python versions earlier than Python 3.10 allowed using both <code class="docutils literal notranslate">;</code> and <code class="docutils literal notranslate">&amp;</code> as
query parameter separators in <a class="reference internal" href="../library/urllib.parse.html#urllib.parse.parse_qs" title="urllib.parse.parse_qs"><code class="xref py py-func docutils literal notranslate">urllib.parse.parse_qs()</code></a> and
<a class="reference internal" href="../library/urllib.parse.html#urllib.parse.parse_qsl" title="urllib.parse.parse_qsl"><code class="xref py py-func docutils literal notranslate">urllib.parse.parse_qsl()</code></a>. Due to security concerns, and to conform with
newer W3C recommendations, this has been changed to allow only a single
separator key, with <code class="docutils literal notranslate">&amp;</code> as the default. This change also affects
<a class="reference internal" href="../library/cgi.html#cgi.parse" title="cgi.parse"><code class="xref py py-func docutils literal notranslate">cgi.parse()</code></a> and <a class="reference internal" href="../library/cgi.html#cgi.parse_multipart" title="cgi.parse_multipart"><code class="xref py py-func docutils literal notranslate">cgi.parse_multipart()</code></a> as they use the affected
functions internally. For more details, please see their respective
documentation.
(Contributed by Adam Goldschmidt, Senthil Kumaran and Ken Jin in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42967">bpo-42967</a>.)
The presence of newline or tab characters in parts of a URL allows for some
forms of attacks. Following the WHATWG specification that updates <a class="rfc reference external" href="https://datatracker.ietf.org/doc/html/rfc3986.html">RFC 3986</a>,
ASCII newline <code class="docutils literal notranslate">\n</code>, <code class="docutils literal notranslate">\r</code> and tab <code class="docutils literal notranslate">\t</code> characters are stripped from the
URL by the parser in <a class="reference internal" href="../library/urllib.parse.html#module-urllib.parse" title="urllib.parse: Parse URLs into or assemble them from components."><code class="xref py py-mod docutils literal notranslate">urllib.parse</code></a> preventing such attacks. The removal
characters are controlled by a new module level variable
<code class="docutils literal notranslate">urllib.parse._UNSAFE_URL_BYTES_TO_REMOVE</code>. (See <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43882">bpo-43882</a>)
</section>
<section id="xml">
<h3>xml<a class="headerlink" href="#xml" title="Permalink to this headline">¶</a></h3>
Add a <a class="reference internal" href="../library/xml.sax.handler.html#xml.sax.handler.LexicalHandler" title="xml.sax.handler.LexicalHandler"><code class="xref py py-class docutils literal notranslate">LexicalHandler</code></a> class to the
<a class="reference internal" href="../library/xml.sax.handler.html#module-xml.sax.handler" title="xml.sax.handler: Base classes for SAX event handlers."><code class="xref py py-mod docutils literal notranslate">xml.sax.handler</code></a> module.
(Contributed by Jonathan Gossage and Zackery Spytz in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=35018">bpo-35018</a>.)
</section>
<section id="zipimport">
<h3>zipimport<a class="headerlink" href="#zipimport" title="Permalink to this headline">¶</a></h3>
Add methods related to <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0451">PEP 451</a>: <a class="reference internal" href="../library/zipimport.html#zipimport.zipimporter.find_spec" title="zipimport.zipimporter.find_spec"><code class="xref py py-meth docutils literal notranslate">find_spec()</code></a>,
<a class="reference internal" href="../library/zipimport.html#zipimport.zipimporter.create_module" title="zipimport.zipimporter.create_module"><code class="xref py py-meth docutils literal notranslate">zipimport.zipimporter.create_module()</code></a>, and
<a class="reference internal" href="../library/zipimport.html#zipimport.zipimporter.exec_module" title="zipimport.zipimporter.exec_module"><code class="xref py py-meth docutils literal notranslate">zipimport.zipimporter.exec_module()</code></a>.
(Contributed by Brett Cannon in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42131">bpo-42131</a>.)
Add <a class="reference internal" href="../library/zipimport.html#zipimport.zipimporter.invalidate_caches" title="zipimport.zipimporter.invalidate_caches"><code class="xref py py-meth docutils literal notranslate">invalidate_caches()</code></a> method.
(Contributed by Desmond Cheong in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=14678">bpo-14678</a>.)
</section>
</section>
<section id="optimizations">
<h2>Optimizations<a class="headerlink" href="#optimizations" title="Permalink to this headline">¶</a></h2>
<ul class="simple">
<li>Constructors <a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-func docutils literal notranslate">str()</code></a>, <a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-func docutils literal notranslate">bytes()</code></a> and <a class="reference internal" href="../library/stdtypes.html#bytearray" title="bytearray"><code class="xref py py-func docutils literal notranslate">bytearray()</code></a> are now faster
(around 30–40% for small objects).
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41334">bpo-41334</a>.)</li>
<li>The <a class="reference internal" href="../library/runpy.html#module-runpy" title="runpy: Locate and run Python modules without importing them first."><code class="xref py py-mod docutils literal notranslate">runpy</code></a> module now imports fewer modules.
The <code class="docutils literal notranslate">python3 -m module-name</code> command startup time is 1.4x faster in
average. On Linux, <code class="docutils literal notranslate">python3 -I -m module-name</code> imports 69 modules on Python
3.9, whereas it only imports 51 modules (-18) on Python 3.10.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41006">bpo-41006</a> and <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41718">bpo-41718</a>.)</li>
<li>The <code class="docutils literal notranslate">LOAD_ATTR</code> instruction now uses new “per opcode cache” mechanism. It
is about 36% faster now for regular attributes and 44% faster for slots.
(Contributed by Pablo Galindo and Yury Selivanov in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42093">bpo-42093</a> and Guido
van Rossum in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42927">bpo-42927</a>, based on ideas implemented originally in PyPy
and MicroPython.)</li>
<li>When building Python with <a class="reference internal" href="../using/configure.html#cmdoption-enable-optimizations"><code class="xref std std-option docutils literal notranslate">--enable-optimizations</code></a> now
<code class="docutils literal notranslate">-fno-semantic-interposition</code> is added to both the compile and link line.
This speeds builds of the Python interpreter created with <a class="reference internal" href="../using/configure.html#cmdoption-enable-shared"><code class="xref std std-option docutils literal notranslate">--enable-shared</code></a>
with <code class="docutils literal notranslate">gcc</code> by up to 30%. See <a class="reference external" href="https://developers.redhat.com/blog/2020/06/25/red-hat-enterprise-linux-8-2-brings-faster-python-3-8-run-speeds/">this article</a>
for more details. (Contributed by Victor Stinner and Pablo Galindo in
<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=38980">bpo-38980</a>.)</li>
<li>Use a new output buffer management code for <a class="reference internal" href="../library/bz2.html#module-bz2" title="bz2: Interfaces for bzip2 compression and decompression."><code class="xref py py-mod docutils literal notranslate">bz2</code></a> / <a class="reference internal" href="../library/lzma.html#module-lzma" title="lzma: A Python wrapper for the liblzma compression library."><code class="xref py py-mod docutils literal notranslate">lzma</code></a> /
<a class="reference internal" href="../library/zlib.html#module-zlib" title="zlib: Low-level interface to compression and decompression routines compatible with gzip."><code class="xref py py-mod docutils literal notranslate">zlib</code></a> modules, and add <code class="docutils literal notranslate">.readall()</code> function to
<code class="docutils literal notranslate">_compression.DecompressReader</code> class. bz2 decompression is now 1.09x ~ 1.17x
faster, lzma decompression 1.20x ~ 1.32x faster, <code class="docutils literal notranslate">GzipFile.read(-1)</code> 1.11x
~ 1.18x faster. (Contributed by Ma Lin, reviewed by Gregory P. Smith, in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41486">bpo-41486</a>)</li>
<li>When using stringized annotations, annotations dicts for functions are no longer
created when the function is created. Instead, they are stored as a tuple of
strings, and the function object lazily converts this into the annotations dict
on demand. This optimization cuts the CPU time needed to define an annotated
function by half.
(Contributed by Yurii Karabas and Inada Naoki in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42202">bpo-42202</a>.)</li>
<li>Substring search functions such as <code class="docutils literal notranslate">str1 in str2</code> and <code class="docutils literal notranslate">str2.find(str1)</code>
now sometimes use Crochemore &amp; Perrin’s “Two-Way” string searching
algorithm to avoid quadratic behavior on long strings. (Contributed
by Dennis Sweeney in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41972">bpo-41972</a>)</li>
<li>Add micro-optimizations to <code class="docutils literal notranslate">_PyType_Lookup()</code> to improve type attribute cache lookup
performance in the common case of cache hits. This makes the interpreter 1.04 times faster
on average. (Contributed by Dino Viehland in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43452">bpo-43452</a>.)</li>
<li>The following built-in functions now support the faster <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0590">PEP 590</a> vectorcall calling convention:
<a class="reference internal" href="../library/functions.html#map" title="map"><code class="xref py py-func docutils literal notranslate">map()</code></a>, <a class="reference internal" href="../library/functions.html#filter" title="filter"><code class="xref py py-func docutils literal notranslate">filter()</code></a>, <a class="reference internal" href="../library/functions.html#reversed" title="reversed"><code class="xref py py-func docutils literal notranslate">reversed()</code></a>, <a class="reference internal" href="../library/functions.html#bool" title="bool"><code class="xref py py-func docutils literal notranslate">bool()</code></a> and <a class="reference internal" href="../library/functions.html#float" title="float"><code class="xref py py-func docutils literal notranslate">float()</code></a>.
(Contributed by Dong-hee Na and Jeroen Demeyer in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43575">bpo-43575</a>, <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43287">bpo-43287</a>, <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41922">bpo-41922</a>, <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41873">bpo-41873</a> and <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41870">bpo-41870</a>.)</li>
<li><code class="xref py py-class docutils literal notranslate">BZ2File</code> performance is improved by removing internal <code class="docutils literal notranslate">RLock</code>.
This makes <code class="xref py py-class docutils literal notranslate">BZ2File</code> thread unsafe in the face of multiple simultaneous
readers or writers, just like its equivalent classes in <a class="reference internal" href="../library/gzip.html#module-gzip" title="gzip: Interfaces for gzip compression and decompression using file objects."><code class="xref py py-mod docutils literal notranslate">gzip</code></a> and
<a class="reference internal" href="../library/lzma.html#module-lzma" title="lzma: A Python wrapper for the liblzma compression library."><code class="xref py py-mod docutils literal notranslate">lzma</code></a> have always been. (Contributed by Inada Naoki in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43785">bpo-43785</a>.)</li>
</ul>
</section>
<section id="deprecated">
<h2>Deprecated<a class="headerlink" href="#deprecated" title="Permalink to this headline">¶</a></h2>
<ul>
<li>Currently Python accepts numeric literals immediately followed by keywords,
for example <code class="docutils literal notranslate">0in x</code>, <code class="docutils literal notranslate">1or x</code>, <code class="docutils literal notranslate">0if 1else 2</code>. It allows confusing
and ambiguous expressions like <code class="docutils literal notranslate">[0x1for x in y]</code> (which can be
interpreted as <code class="docutils literal notranslate">[0x1 for x in y]</code> or <code class="docutils literal notranslate">[0x1f or x in y]</code>). Starting in
this release, a deprecation warning is raised if the numeric literal is
immediately followed by one of keywords <a class="reference internal" href="../reference/expressions.html#and"><code class="xref std std-keyword docutils literal notranslate">and</code></a>, <a class="reference internal" href="../reference/compound_stmts.html#else"><code class="xref std std-keyword docutils literal notranslate">else</code></a>,
<a class="reference internal" href="../reference/compound_stmts.html#for"><code class="xref std std-keyword docutils literal notranslate">for</code></a>, <a class="reference internal" href="../reference/compound_stmts.html#if"><code class="xref std std-keyword docutils literal notranslate">if</code></a>, <a class="reference internal" href="../reference/expressions.html#in"><code class="xref std std-keyword docutils literal notranslate">in</code></a>, <a class="reference internal" href="../reference/expressions.html#is"><code class="xref std std-keyword docutils literal notranslate">is</code></a> and <a class="reference internal" href="../reference/expressions.html#or"><code class="xref std std-keyword docutils literal notranslate">or</code></a>.
In future releases it will be changed to syntax warning, and finally to
syntax error.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43833">bpo-43833</a>.)</li>
<li>Starting in this release, there will be a concerted effort to begin
cleaning up old import semantics that were kept for Python 2.7
compatibility. Specifically,
<a class="reference internal" href="../library/importlib.html#importlib.abc.PathEntryFinder.find_loader" title="importlib.abc.PathEntryFinder.find_loader"><code class="xref py py-meth docutils literal notranslate">find_loader()</code></a>/<a class="reference internal" href="../library/importlib.html#importlib.abc.Finder.find_module" title="importlib.abc.Finder.find_module"><code class="xref py py-meth docutils literal notranslate">find_module()</code></a>
(superseded by <code class="xref py py-meth docutils literal notranslate">find_spec()</code>),
<a class="reference internal" href="../library/importlib.html#importlib.abc.Loader.load_module" title="importlib.abc.Loader.load_module"><code class="xref py py-meth docutils literal notranslate">load_module()</code></a>
(superseded by <a class="reference internal" href="../library/importlib.html#importlib.abc.Loader.exec_module" title="importlib.abc.Loader.exec_module"><code class="xref py py-meth docutils literal notranslate">exec_module()</code></a>),
<a class="reference internal" href="../library/importlib.html#importlib.abc.Loader.module_repr" title="importlib.abc.Loader.module_repr"><code class="xref py py-meth docutils literal notranslate">module_repr()</code></a> (which the import system
takes care of for you), the <code class="docutils literal notranslate">__package__</code> attribute
(superseded by <code class="docutils literal notranslate">__spec__.parent</code>), the <code class="docutils literal notranslate">__loader__</code> attribute
(superseded by <code class="docutils literal notranslate">__spec__.loader</code>), and the <code class="docutils literal notranslate">__cached__</code> attribute
(superseded by <code class="docutils literal notranslate">__spec__.cached</code>) will slowly be removed (as well
as other classes and methods in <a class="reference internal" href="../library/importlib.html#module-importlib" title="importlib: The implementation of the import machinery."><code class="xref py py-mod docutils literal notranslate">importlib</code></a>).
<a class="reference internal" href="../library/exceptions.html#ImportWarning" title="ImportWarning"><code class="xref py py-exc docutils literal notranslate">ImportWarning</code></a> and/or <a class="reference internal" href="../library/exceptions.html#DeprecationWarning" title="DeprecationWarning"><code class="xref py py-exc docutils literal notranslate">DeprecationWarning</code></a> will be raised
as appropriate to help identify code which needs updating during
this transition.</li>
<li>The entire <code class="docutils literal notranslate">distutils</code> namespace is deprecated, to be removed in
Python 3.12. Refer to the <a class="reference internal" href="#distutils-deprecated">module changes</a>
section for more information.</li>
<li>Non-integer arguments to <a class="reference internal" href="../library/random.html#random.randrange" title="random.randrange"><code class="xref py py-func docutils literal notranslate">random.randrange()</code></a> are deprecated.
The <a class="reference internal" href="../library/exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate">ValueError</code></a> is deprecated in favor of a <a class="reference internal" href="../library/exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate">TypeError</code></a>.
(Contributed by Serhiy Storchaka and Raymond Hettinger in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=37319">bpo-37319</a>.)</li>
<li>The various <code class="docutils literal notranslate">load_module()</code> methods of <a class="reference internal" href="../library/importlib.html#module-importlib" title="importlib: The implementation of the import machinery."><code class="xref py py-mod docutils literal notranslate">importlib</code></a> have been
documented as deprecated since Python 3.6, but will now also trigger
a <a class="reference internal" href="../library/exceptions.html#DeprecationWarning" title="DeprecationWarning"><code class="xref py py-exc docutils literal notranslate">DeprecationWarning</code></a>. Use
<a class="reference internal" href="../library/importlib.html#importlib.abc.Loader.exec_module" title="importlib.abc.Loader.exec_module"><code class="xref py py-meth docutils literal notranslate">exec_module()</code></a> instead.
(Contributed by Brett Cannon in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=26131">bpo-26131</a>.)</li>
<li><code class="xref py py-meth docutils literal notranslate">zimport.zipimporter.load_module()</code> has been deprecated in
preference for <a class="reference internal" href="../library/zipimport.html#zipimport.zipimporter.exec_module" title="zipimport.zipimporter.exec_module"><code class="xref py py-meth docutils literal notranslate">exec_module()</code></a>.
(Contributed by Brett Cannon in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=26131">bpo-26131</a>.)</li>
<li>The use of <a class="reference internal" href="../library/importlib.html#importlib.abc.Loader.load_module" title="importlib.abc.Loader.load_module"><code class="xref py py-meth docutils literal notranslate">load_module()</code></a> by the import
system now triggers an <a class="reference internal" href="../library/exceptions.html#ImportWarning" title="ImportWarning"><code class="xref py py-exc docutils literal notranslate">ImportWarning</code></a> as
<a class="reference internal" href="../library/importlib.html#importlib.abc.Loader.exec_module" title="importlib.abc.Loader.exec_module"><code class="xref py py-meth docutils literal notranslate">exec_module()</code></a> is preferred.
(Contributed by Brett Cannon in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=26131">bpo-26131</a>.)</li>
<li>The use of <a class="reference internal" href="../library/importlib.html#importlib.abc.MetaPathFinder.find_module" title="importlib.abc.MetaPathFinder.find_module"><code class="xref py py-meth docutils literal notranslate">importlib.abc.MetaPathFinder.find_module()</code></a> and
<a class="reference internal" href="../library/importlib.html#importlib.abc.PathEntryFinder.find_module" title="importlib.abc.PathEntryFinder.find_module"><code class="xref py py-meth docutils literal notranslate">importlib.abc.PathEntryFinder.find_module()</code></a> by the import system now
trigger an <a class="reference internal" href="../library/exceptions.html#ImportWarning" title="ImportWarning"><code class="xref py py-exc docutils literal notranslate">ImportWarning</code></a> as
<a class="reference internal" href="../library/importlib.html#importlib.abc.MetaPathFinder.find_spec" title="importlib.abc.MetaPathFinder.find_spec"><code class="xref py py-meth docutils literal notranslate">importlib.abc.MetaPathFinder.find_spec()</code></a> and
<a class="reference internal" href="../library/importlib.html#importlib.abc.PathEntryFinder.find_spec" title="importlib.abc.PathEntryFinder.find_spec"><code class="xref py py-meth docutils literal notranslate">importlib.abc.PathEntryFinder.find_spec()</code></a>
are preferred, respectively. You can use
<a class="reference internal" href="../library/importlib.html#importlib.util.spec_from_loader" title="importlib.util.spec_from_loader"><code class="xref py py-func docutils literal notranslate">importlib.util.spec_from_loader()</code></a> to help in porting.
(Contributed by Brett Cannon in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42134">bpo-42134</a>.)</li>
<li>The use of <a class="reference internal" href="../library/importlib.html#importlib.abc.PathEntryFinder.find_loader" title="importlib.abc.PathEntryFinder.find_loader"><code class="xref py py-meth docutils literal notranslate">importlib.abc.PathEntryFinder.find_loader()</code></a> by the import
system now triggers an <a class="reference internal" href="../library/exceptions.html#ImportWarning" title="ImportWarning"><code class="xref py py-exc docutils literal notranslate">ImportWarning</code></a> as
<a class="reference internal" href="../library/importlib.html#importlib.abc.PathEntryFinder.find_spec" title="importlib.abc.PathEntryFinder.find_spec"><code class="xref py py-meth docutils literal notranslate">importlib.abc.PathEntryFinder.find_spec()</code></a> is preferred. You can use
<a class="reference internal" href="../library/importlib.html#importlib.util.spec_from_loader" title="importlib.util.spec_from_loader"><code class="xref py py-func docutils literal notranslate">importlib.util.spec_from_loader()</code></a> to help in porting.
(Contributed by Brett Cannon in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43672">bpo-43672</a>.)</li>
<li>The various implementations of
<a class="reference internal" href="../library/importlib.html#importlib.abc.MetaPathFinder.find_module" title="importlib.abc.MetaPathFinder.find_module"><code class="xref py py-meth docutils literal notranslate">importlib.abc.MetaPathFinder.find_module()</code></a> (
<code class="xref py py-meth docutils literal notranslate">importlib.machinery.BuiltinImporter.find_module()</code>,
<code class="xref py py-meth docutils literal notranslate">importlib.machinery.FrozenImporter.find_module()</code>,
<code class="xref py py-meth docutils literal notranslate">importlib.machinery.WindowsRegistryFinder.find_module()</code>,
<a class="reference internal" href="../library/importlib.html#importlib.machinery.PathFinder.find_module" title="importlib.machinery.PathFinder.find_module"><code class="xref py py-meth docutils literal notranslate">importlib.machinery.PathFinder.find_module()</code></a>,
<a class="reference internal" href="../library/importlib.html#importlib.abc.MetaPathFinder.find_module" title="importlib.abc.MetaPathFinder.find_module"><code class="xref py py-meth docutils literal notranslate">importlib.abc.MetaPathFinder.find_module()</code></a> ),
<a class="reference internal" href="../library/importlib.html#importlib.abc.PathEntryFinder.find_module" title="importlib.abc.PathEntryFinder.find_module"><code class="xref py py-meth docutils literal notranslate">importlib.abc.PathEntryFinder.find_module()</code></a> (
<code class="xref py py-meth docutils literal notranslate">importlib.machinery.FileFinder.find_module()</code> ), and
<a class="reference internal" href="../library/importlib.html#importlib.abc.PathEntryFinder.find_loader" title="importlib.abc.PathEntryFinder.find_loader"><code class="xref py py-meth docutils literal notranslate">importlib.abc.PathEntryFinder.find_loader()</code></a> (
<a class="reference internal" href="../library/importlib.html#importlib.machinery.FileFinder.find_loader" title="importlib.machinery.FileFinder.find_loader"><code class="xref py py-meth docutils literal notranslate">importlib.machinery.FileFinder.find_loader()</code></a> )
now raise <a class="reference internal" href="../library/exceptions.html#DeprecationWarning" title="DeprecationWarning"><code class="xref py py-exc docutils literal notranslate">DeprecationWarning</code></a> and are slated for removal in
Python 3.12 (previously they were documented as deprecated in Python 3.4).
(Contributed by Brett Cannon in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42135">bpo-42135</a>.)</li>
<li><a class="reference internal" href="../library/importlib.html#importlib.abc.Finder" title="importlib.abc.Finder"><code class="xref py py-class docutils literal notranslate">importlib.abc.Finder</code></a> is deprecated (including its sole method,
<a class="reference internal" href="../library/importlib.html#importlib.abc.Finder.find_module" title="importlib.abc.Finder.find_module"><code class="xref py py-meth docutils literal notranslate">find_module()</code></a>). Both
<a class="reference internal" href="../library/importlib.html#importlib.abc.MetaPathFinder" title="importlib.abc.MetaPathFinder"><code class="xref py py-class docutils literal notranslate">importlib.abc.MetaPathFinder</code></a> and <a class="reference internal" href="../library/importlib.html#importlib.abc.PathEntryFinder" title="importlib.abc.PathEntryFinder"><code class="xref py py-class docutils literal notranslate">importlib.abc.PathEntryFinder</code></a>
no longer inherit from the class. Users should inherit from one of these two
classes as appropriate instead.
(Contributed by Brett Cannon in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42135">bpo-42135</a>.)</li>
<li>The deprecations of <a class="reference internal" href="../library/imp.html#module-imp" title="imp: Access the implementation of the import statement. (deprecated)"><code class="xref py py-mod docutils literal notranslate">imp</code></a>, <a class="reference internal" href="../library/importlib.html#importlib.find_loader" title="importlib.find_loader"><code class="xref py py-func docutils literal notranslate">importlib.find_loader()</code></a>,
<code class="xref py py-func docutils literal notranslate">importlib.util.set_package_wrapper()</code>,
<code class="xref py py-func docutils literal notranslate">importlib.util.set_loader_wrapper()</code>,
<a class="reference internal" href="../library/importlib.html#importlib.util.module_for_loader" title="importlib.util.module_for_loader"><code class="xref py py-func docutils literal notranslate">importlib.util.module_for_loader()</code></a>,
<a class="reference internal" href="../library/pkgutil.html#pkgutil.ImpImporter" title="pkgutil.ImpImporter"><code class="xref py py-class docutils literal notranslate">pkgutil.ImpImporter</code></a>, and
<a class="reference internal" href="../library/pkgutil.html#pkgutil.ImpLoader" title="pkgutil.ImpLoader"><code class="xref py py-class docutils literal notranslate">pkgutil.ImpLoader</code></a> have all been updated to list Python 3.12 as the
slated version of removal (they began raising <a class="reference internal" href="../library/exceptions.html#DeprecationWarning" title="DeprecationWarning"><code class="xref py py-exc docutils literal notranslate">DeprecationWarning</code></a> in
previous versions of Python).
(Contributed by Brett Cannon in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43720">bpo-43720</a>.)</li>
<li>The import system now uses the <code class="docutils literal notranslate">__spec__</code> attribute on modules before
falling back on <a class="reference internal" href="../library/importlib.html#importlib.abc.Loader.module_repr" title="importlib.abc.Loader.module_repr"><code class="xref py py-meth docutils literal notranslate">module_repr()</code></a> for a module’s
<code class="docutils literal notranslate">__repr__()</code> method. Removal of the use of <code class="docutils literal notranslate">module_repr()</code> is scheduled
for Python 3.12.
(Contributed by Brett Cannon in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42137">bpo-42137</a>.)</li>
<li><a class="reference internal" href="../library/importlib.html#importlib.abc.Loader.module_repr" title="importlib.abc.Loader.module_repr"><code class="xref py py-meth docutils literal notranslate">importlib.abc.Loader.module_repr()</code></a>,
<code class="xref py py-meth docutils literal notranslate">importlib.machinery.FrozenLoader.module_repr()</code>, and
<code class="xref py py-meth docutils literal notranslate">importlib.machinery.BuiltinLoader.module_repr()</code> are deprecated and
slated for removal in Python 3.12.
(Contributed by Brett Cannon in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42136">bpo-42136</a>.)</li>
<li><code class="docutils literal notranslate">sqlite3.OptimizedUnicode</code> has been undocumented and obsolete since Python
3.3, when it was made an alias to <a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a>. It is now deprecated,
scheduled for removal in Python 3.12.
(Contributed by Erlend E. Aasland in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42264">bpo-42264</a>.)</li>
<li>The undocumented built-in function <code class="docutils literal notranslate">sqlite3.enable_shared_cache</code> is now
deprecated, scheduled for removal in Python 3.12. Its use is strongly
discouraged by the SQLite3 documentation. See <a class="reference external" href="https://sqlite.org/c3ref/enable_shared_cache.html">the SQLite3 docs</a> for more details.
If a shared cache must be used, open the database in URI mode using the
<code class="docutils literal notranslate">cache=shared</code> query parameter.
(Contributed by Erlend E. Aasland in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=24464">bpo-24464</a>.)</li>
<li>The following <code class="docutils literal notranslate">threading</code> methods are now deprecated:
<ul class="simple">
<li><code class="docutils literal notranslate">threading.currentThread</code> =&gt; <a class="reference internal" href="../library/threading.html#threading.current_thread" title="threading.current_thread"><code class="xref py py-func docutils literal notranslate">threading.current_thread()</code></a></li>
<li><code class="docutils literal notranslate">threading.activeCount</code> =&gt; <a class="reference internal" href="../library/threading.html#threading.active_count" title="threading.active_count"><code class="xref py py-func docutils literal notranslate">threading.active_count()</code></a></li>
<li><code class="docutils literal notranslate">threading.Condition.notifyAll</code> =&gt;
<a class="reference internal" href="../library/threading.html#threading.Condition.notify_all" title="threading.Condition.notify_all"><code class="xref py py-meth docutils literal notranslate">threading.Condition.notify_all()</code></a></li>
<li><code class="docutils literal notranslate">threading.Event.isSet</code> =&gt; <a class="reference internal" href="../library/threading.html#threading.Event.is_set" title="threading.Event.is_set"><code class="xref py py-meth docutils literal notranslate">threading.Event.is_set()</code></a></li>
<li><code class="docutils literal notranslate">threading.Thread.setName</code> =&gt; <a class="reference internal" href="../library/threading.html#threading.Thread.name" title="threading.Thread.name"><code class="xref py py-attr docutils literal notranslate">threading.Thread.name</code></a></li>
<li><code class="docutils literal notranslate">threading.thread.getName</code> =&gt; <a class="reference internal" href="../library/threading.html#threading.Thread.name" title="threading.Thread.name"><code class="xref py py-attr docutils literal notranslate">threading.Thread.name</code></a></li>
<li><code class="docutils literal notranslate">threading.Thread.isDaemon</code> =&gt; <a class="reference internal" href="../library/threading.html#threading.Thread.daemon" title="threading.Thread.daemon"><code class="xref py py-attr docutils literal notranslate">threading.Thread.daemon</code></a></li>
<li><code class="docutils literal notranslate">threading.Thread.setDaemon</code> =&gt; <a class="reference internal" href="../library/threading.html#threading.Thread.daemon" title="threading.Thread.daemon"><code class="xref py py-attr docutils literal notranslate">threading.Thread.daemon</code></a></li>
</ul>
(Contributed by Jelle Zijlstra in <a class="reference external" href="https://github.com/python/cpython/issues/87889">gh-87889</a>.)
</li>
<li><a class="reference internal" href="../library/pathlib.html#pathlib.Path.link_to" title="pathlib.Path.link_to"><code class="xref py py-meth docutils literal notranslate">pathlib.Path.link_to()</code></a> is deprecated and slated for removal in
Python 3.12. Use <a class="reference internal" href="../library/pathlib.html#pathlib.Path.hardlink_to" title="pathlib.Path.hardlink_to"><code class="xref py py-meth docutils literal notranslate">pathlib.Path.hardlink_to()</code></a> instead.
(Contributed by Barney Gale in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=39950">bpo-39950</a>.)</li>
<li><code class="docutils literal notranslate">cgi.log()</code> is deprecated and slated for removal in Python 3.12.
(Contributed by Inada Naoki in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41139">bpo-41139</a>.)</li>
<li>The following <a class="reference internal" href="../library/ssl.html#module-ssl" title="ssl: TLS/SSL wrapper for socket objects"><code class="xref py py-mod docutils literal notranslate">ssl</code></a> features have been deprecated since Python 3.6,
Python 3.7, or OpenSSL 1.1.0 and will be removed in 3.11:
<ul class="simple">
<li><a class="reference internal" href="../library/ssl.html#ssl.OP_NO_SSLv2" title="ssl.OP_NO_SSLv2"><code class="xref py py-data docutils literal notranslate">OP_NO_SSLv2</code></a>, <a class="reference internal" href="../library/ssl.html#ssl.OP_NO_SSLv3" title="ssl.OP_NO_SSLv3"><code class="xref py py-data docutils literal notranslate">OP_NO_SSLv3</code></a>, <a class="reference internal" href="../library/ssl.html#ssl.OP_NO_TLSv1" title="ssl.OP_NO_TLSv1"><code class="xref py py-data docutils literal notranslate">OP_NO_TLSv1</code></a>,
<a class="reference internal" href="../library/ssl.html#ssl.OP_NO_TLSv1_1" title="ssl.OP_NO_TLSv1_1"><code class="xref py py-data docutils literal notranslate">OP_NO_TLSv1_1</code></a>, <a class="reference internal" href="../library/ssl.html#ssl.OP_NO_TLSv1_2" title="ssl.OP_NO_TLSv1_2"><code class="xref py py-data docutils literal notranslate">OP_NO_TLSv1_2</code></a>, and
<a class="reference internal" href="../library/ssl.html#ssl.OP_NO_TLSv1_3" title="ssl.OP_NO_TLSv1_3"><code class="xref py py-data docutils literal notranslate">OP_NO_TLSv1_3</code></a> are replaced by
<code class="xref py py-attr docutils literal notranslate">sslSSLContext.minimum_version</code> and
<code class="xref py py-attr docutils literal notranslate">sslSSLContext.maximum_version</code>.</li>
<li><a class="reference internal" href="../library/ssl.html#ssl.PROTOCOL_SSLv2" title="ssl.PROTOCOL_SSLv2"><code class="xref py py-data docutils literal notranslate">PROTOCOL_SSLv2</code></a>, <a class="reference internal" href="../library/ssl.html#ssl.PROTOCOL_SSLv3" title="ssl.PROTOCOL_SSLv3"><code class="xref py py-data docutils literal notranslate">PROTOCOL_SSLv3</code></a>,
<a class="reference internal" href="../library/ssl.html#ssl.PROTOCOL_SSLv23" title="ssl.PROTOCOL_SSLv23"><code class="xref py py-data docutils literal notranslate">PROTOCOL_SSLv23</code></a>, <a class="reference internal" href="../library/ssl.html#ssl.PROTOCOL_TLSv1" title="ssl.PROTOCOL_TLSv1"><code class="xref py py-data docutils literal notranslate">PROTOCOL_TLSv1</code></a>,
<a class="reference internal" href="../library/ssl.html#ssl.PROTOCOL_TLSv1_1" title="ssl.PROTOCOL_TLSv1_1"><code class="xref py py-data docutils literal notranslate">PROTOCOL_TLSv1_1</code></a>, <a class="reference internal" href="../library/ssl.html#ssl.PROTOCOL_TLSv1_2" title="ssl.PROTOCOL_TLSv1_2"><code class="xref py py-data docutils literal notranslate">PROTOCOL_TLSv1_2</code></a>, and
<a class="reference internal" href="../library/ssl.html#ssl.PROTOCOL_TLS" title="ssl.PROTOCOL_TLS"><code class="xref py py-data docutils literal notranslate">PROTOCOL_TLS</code></a> are deprecated in favor of
<a class="reference internal" href="../library/ssl.html#ssl.PROTOCOL_TLS_CLIENT" title="ssl.PROTOCOL_TLS_CLIENT"><code class="xref py py-data docutils literal notranslate">PROTOCOL_TLS_CLIENT</code></a> and <a class="reference internal" href="../library/ssl.html#ssl.PROTOCOL_TLS_SERVER" title="ssl.PROTOCOL_TLS_SERVER"><code class="xref py py-data docutils literal notranslate">PROTOCOL_TLS_SERVER</code></a></li>
<li><a class="reference internal" href="../library/ssl.html#ssl.wrap_socket" title="ssl.wrap_socket"><code class="xref py py-func docutils literal notranslate">wrap_socket()</code></a> is replaced by <a class="reference internal" href="../library/ssl.html#ssl.SSLContext.wrap_socket" title="ssl.SSLContext.wrap_socket"><code class="xref py py-meth docutils literal notranslate">ssl.SSLContext.wrap_socket()</code></a></li>
<li><a class="reference internal" href="../library/ssl.html#ssl.match_hostname" title="ssl.match_hostname"><code class="xref py py-func docutils literal notranslate">match_hostname()</code></a></li>
<li><a class="reference internal" href="../library/ssl.html#ssl.RAND_pseudo_bytes" title="ssl.RAND_pseudo_bytes"><code class="xref py py-func docutils literal notranslate">RAND_pseudo_bytes()</code></a>, <code class="xref py py-func docutils literal notranslate">RAND_egd()</code></li>
<li>NPN features like <a class="reference internal" href="../library/ssl.html#ssl.SSLSocket.selected_npn_protocol" title="ssl.SSLSocket.selected_npn_protocol"><code class="xref py py-meth docutils literal notranslate">ssl.SSLSocket.selected_npn_protocol()</code></a> and
<a class="reference internal" href="../library/ssl.html#ssl.SSLContext.set_npn_protocols" title="ssl.SSLContext.set_npn_protocols"><code class="xref py py-meth docutils literal notranslate">ssl.SSLContext.set_npn_protocols()</code></a> are replaced by ALPN.</li>
</ul>
</li>
<li>The threading debug (<a class="reference internal" href="../using/cmdline.html#envvar-PYTHONTHREADDEBUG"><code class="xref std std-envvar docutils literal notranslate">PYTHONTHREADDEBUG</code></a> environment variable) is
deprecated in Python 3.10 and will be removed in Python 3.12. This feature
requires a <a class="reference internal" href="../using/configure.html#debug-build">debug build of Python</a>.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=44584">bpo-44584</a>.)</li>
<li>Importing from the <code class="docutils literal notranslate">typing.io</code> and <code class="docutils literal notranslate">typing.re</code> submodules will now emit
<a class="reference internal" href="../library/exceptions.html#DeprecationWarning" title="DeprecationWarning"><code class="xref py py-exc docutils literal notranslate">DeprecationWarning</code></a>. These submodules will be removed in a future version
of Python. Anything belonging to these submodules should be imported directly
from <a class="reference internal" href="../library/typing.html#module-typing" title="typing: Support for type hints (see :pep:`484`)."><code class="xref py py-mod docutils literal notranslate">typing</code></a> instead.
(Contributed by Sebastian Rittau in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=38291">bpo-38291</a>.)</li>
</ul>
</section>
<section id="removed">
<h2>Removed<a class="headerlink" href="#removed" title="Permalink to this headline">¶</a></h2>
<ul>
<li>Removed special methods <code class="docutils literal notranslate">__int__</code>, <code class="docutils literal notranslate">__float__</code>, <code class="docutils literal notranslate">__floordiv__</code>,
<code class="docutils literal notranslate">__mod__</code>, <code class="docutils literal notranslate">__divmod__</code>, <code class="docutils literal notranslate">__rfloordiv__</code>, <code class="docutils literal notranslate">__rmod__</code> and
<code class="docutils literal notranslate">__rdivmod__</code> of the <a class="reference internal" href="../library/functions.html#complex" title="complex"><code class="xref py py-class docutils literal notranslate">complex</code></a> class. They always raised
a <a class="reference internal" href="../library/exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate">TypeError</code></a>.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41974">bpo-41974</a>.)</li>
<li>The <code class="docutils literal notranslate">ParserBase.error()</code> method from the private and undocumented <code class="docutils literal notranslate">_markupbase</code>
module has been removed. <a class="reference internal" href="../library/html.parser.html#html.parser.HTMLParser" title="html.parser.HTMLParser"><code class="xref py py-class docutils literal notranslate">html.parser.HTMLParser</code></a> is the only subclass of
<code class="docutils literal notranslate">ParserBase</code> and its <code class="docutils literal notranslate">error()</code> implementation was already removed in
Python 3.5.
(Contributed by Berker Peksag in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=31844">bpo-31844</a>.)</li>
<li>Removed the <code class="docutils literal notranslate">unicodedata.ucnhash_CAPI</code> attribute which was an internal
PyCapsule object. The related private <code class="docutils literal notranslate">_PyUnicode_Name_CAPI</code> structure was
moved to the internal C API.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42157">bpo-42157</a>.)</li>
<li>Removed the <code class="docutils literal notranslate">parser</code> module, which was deprecated in 3.9 due to the
switch to the new PEG parser, as well as all the C source and header files
that were only being used by the old parser, including <code class="docutils literal notranslate">node.h</code>, <code class="docutils literal notranslate">parser.h</code>,
<code class="docutils literal notranslate">graminit.h</code> and <code class="docutils literal notranslate">grammar.h</code>.</li>
<li>Removed the Public C API functions <code class="docutils literal notranslate">PyParser_SimpleParseStringFlags</code>,
<code class="docutils literal notranslate">PyParser_SimpleParseStringFlagsFilename</code>,
<code class="docutils literal notranslate">PyParser_SimpleParseFileFlags</code> and <code class="docutils literal notranslate">PyNode_Compile</code>
that were deprecated in 3.9 due to the switch to the new PEG parser.</li>
<li>Removed the <code class="docutils literal notranslate">formatter</code> module, which was deprecated in Python 3.4.
It is somewhat obsolete, little used, and not tested. It was originally
scheduled to be removed in Python 3.6, but such removals were delayed until
after Python 2.7 EOL. Existing users should copy whatever classes they use
into their code.
(Contributed by Dong-hee Na and Terry J. Reedy in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42299">bpo-42299</a>.)</li>
<li>Removed the <code class="xref c c-func docutils literal notranslate">PyModule_GetWarningsModule()</code> function that was useless
now due to the _warnings module was converted to a builtin module in 2.6.
(Contributed by Hai Shi in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42599">bpo-42599</a>.)</li>
<li>Remove deprecated aliases to <a class="reference internal" href="../library/collections.abc.html#collections-abstract-base-classes">Collections Abstract Base Classes</a> from
the <a class="reference internal" href="../library/collections.html#module-collections" title="collections: Container datatypes"><code class="xref py py-mod docutils literal notranslate">collections</code></a> module.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=37324">bpo-37324</a>.)</li>
<li>The <code class="docutils literal notranslate">loop</code> parameter has been removed from most of <a class="reference internal" href="../library/asyncio.html#module-asyncio" title="asyncio: Asynchronous I/O."><code class="xref py py-mod docutils literal notranslate">asyncio</code></a>‘s
<a class="reference internal" href="../library/asyncio-api-index.html">high-level API</a> following deprecation
in Python 3.8. The motivation behind this change is multifold:
<ol class="arabic simple">
<li>This simplifies the high-level API.</li>
<li>The functions in the high-level API have been implicitly getting the
current thread’s running event loop since Python 3.7. There isn’t a need to
pass the event loop to the API in most normal use cases.</li>
<li>Event loop passing is error-prone especially when dealing with loops
running in different threads.</li>
</ol>
Note that the low-level API will still accept <code class="docutils literal notranslate">loop</code>.
See <a class="reference internal" href="#changes-python-api">Changes in the Python API</a> for examples of how to replace existing code.
(Contributed by Yurii Karabas, Andrew Svetlov, Yury Selivanov and Kyle Stanley
in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42392">bpo-42392</a>.)
</li>
</ul>
</section>
<section id="porting-to-python-3-10">
<h2>Porting to Python 3.10<a class="headerlink" href="#porting-to-python-3-10" title="Permalink to this headline">¶</a></h2>
This section lists previously described changes and other bugfixes
that may require changes to your code.
<section id="changes-in-the-python-syntax">
<h3>Changes in the Python syntax<a class="headerlink" href="#changes-in-the-python-syntax" title="Permalink to this headline">¶</a></h3>
<ul class="simple">
<li>Deprecation warning is now emitted when compiling previously valid syntax
if the numeric literal is immediately followed by a keyword (like in <code class="docutils literal notranslate">0in x</code>).
In future releases it will be changed to syntax warning, and finally to a
syntax error. To get rid of the warning and make the code compatible with
future releases just add a space between the numeric literal and the
following keyword.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43833">bpo-43833</a>.)</li>
</ul>
</section>
<section id="changes-in-the-python-api">
<h3>Changes in the Python API<a class="headerlink" href="#changes-in-the-python-api" title="Permalink to this headline">¶</a></h3>
<ul>
<li>The etype parameters of the <a class="reference internal" href="../library/traceback.html#traceback.format_exception" title="traceback.format_exception"><code class="xref py py-func docutils literal notranslate">format_exception()</code></a>,
<a class="reference internal" href="../library/traceback.html#traceback.format_exception_only" title="traceback.format_exception_only"><code class="xref py py-func docutils literal notranslate">format_exception_only()</code></a>, and
<a class="reference internal" href="../library/traceback.html#traceback.print_exception" title="traceback.print_exception"><code class="xref py py-func docutils literal notranslate">print_exception()</code></a> functions in the <a class="reference internal" href="../library/traceback.html#module-traceback" title="traceback: Print or retrieve a stack traceback."><code class="xref py py-mod docutils literal notranslate">traceback</code></a> module
have been renamed to exc.
(Contributed by Zackery Spytz and Matthias Bussonnier in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=26389">bpo-26389</a>.)</li>
<li><a class="reference internal" href="../library/atexit.html#module-atexit" title="atexit: Register and execute cleanup functions."><code class="xref py py-mod docutils literal notranslate">atexit</code></a>: At Python exit, if a callback registered with
<a class="reference internal" href="../library/atexit.html#atexit.register" title="atexit.register"><code class="xref py py-func docutils literal notranslate">atexit.register()</code></a> fails, its exception is now logged. Previously, only
some exceptions were logged, and the last exception was always silently
ignored.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42639">bpo-42639</a>.)</li>
<li><a class="reference internal" href="../library/collections.abc.html#collections.abc.Callable" title="collections.abc.Callable"><code class="xref py py-class docutils literal notranslate">collections.abc.Callable</code></a> generic now flattens type parameters, similar
to what <a class="reference internal" href="../library/typing.html#typing.Callable" title="typing.Callable"><code class="xref py py-data docutils literal notranslate">typing.Callable</code></a> currently does. This means that
<code class="docutils literal notranslate">collections.abc.Callable[[int, str], str]</code> will have <code class="docutils literal notranslate">__args__</code> of
<code class="docutils literal notranslate">(int, str, str)</code>; previously this was <code class="docutils literal notranslate">([int, str], str)</code>. Code which
accesses the arguments via <a class="reference internal" href="../library/typing.html#typing.get_args" title="typing.get_args"><code class="xref py py-func docutils literal notranslate">typing.get_args()</code></a> or <code class="docutils literal notranslate">__args__</code> need to account
for this change. Furthermore, <a class="reference internal" href="../library/exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate">TypeError</code></a> may be raised for invalid forms
of parameterizing <a class="reference internal" href="../library/collections.abc.html#collections.abc.Callable" title="collections.abc.Callable"><code class="xref py py-class docutils literal notranslate">collections.abc.Callable</code></a> which may have passed
silently in Python 3.9.
(Contributed by Ken Jin in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42195">bpo-42195</a>.)</li>
<li><a class="reference internal" href="../library/socket.html#socket.htons" title="socket.htons"><code class="xref py py-meth docutils literal notranslate">socket.htons()</code></a> and <a class="reference internal" href="../library/socket.html#socket.ntohs" title="socket.ntohs"><code class="xref py py-meth docutils literal notranslate">socket.ntohs()</code></a> now raise <a class="reference internal" href="../library/exceptions.html#OverflowError" title="OverflowError"><code class="xref py py-exc docutils literal notranslate">OverflowError</code></a>
instead of <a class="reference internal" href="../library/exceptions.html#DeprecationWarning" title="DeprecationWarning"><code class="xref py py-exc docutils literal notranslate">DeprecationWarning</code></a> if the given parameter will not fit in
a 16-bit unsigned integer.
(Contributed by Erlend E. Aasland in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42393">bpo-42393</a>.)</li>
<li>The <code class="docutils literal notranslate">loop</code> parameter has been removed from most of <a class="reference internal" href="../library/asyncio.html#module-asyncio" title="asyncio: Asynchronous I/O."><code class="xref py py-mod docutils literal notranslate">asyncio</code></a>‘s
<a class="reference internal" href="../library/asyncio-api-index.html">high-level API</a> following deprecation
in Python 3.8.
A coroutine that currently looks like this:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>async def foo(loop):
 await asyncio.sleep(1, loop=loop)
</pre></div>
</div>
Should be replaced with this:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>async def foo():
 await asyncio.sleep(1)
</pre></div>
</div>
If <code class="docutils literal notranslate">foo()</code> was specifically designed not to run in the current thread’s
running event loop (e.g. running in another thread’s event loop), consider
using <a class="reference internal" href="../library/asyncio-task.html#asyncio.run_coroutine_threadsafe" title="asyncio.run_coroutine_threadsafe"><code class="xref py py-func docutils literal notranslate">asyncio.run_coroutine_threadsafe()</code></a> instead.
(Contributed by Yurii Karabas, Andrew Svetlov, Yury Selivanov and Kyle Stanley
in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42392">bpo-42392</a>.)
</li>
<li>The <a class="reference internal" href="../library/types.html#types.FunctionType" title="types.FunctionType"><code class="xref py py-data docutils literal notranslate">types.FunctionType</code></a> constructor now inherits the current builtins
if the globals dictionary has no <code class="docutils literal notranslate">&quot;__builtins__&quot;</code> key, rather than using
<code class="docutils literal notranslate">{&quot;None&quot;: None}</code> as builtins: same behavior as <a class="reference internal" href="../library/functions.html#eval" title="eval"><code class="xref py py-func docutils literal notranslate">eval()</code></a> and
<a class="reference internal" href="../library/functions.html#exec" title="exec"><code class="xref py py-func docutils literal notranslate">exec()</code></a> functions. Defining a function with <code class="docutils literal notranslate">def function(...): ...</code>
in Python is not affected, globals cannot be overridden with this syntax: it
also inherits the current builtins.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42990">bpo-42990</a>.)</li>
</ul>
</section>
<section id="changes-in-the-c-api">
<h3>Changes in the C API<a class="headerlink" href="#changes-in-the-c-api" title="Permalink to this headline">¶</a></h3>
<ul>
<li>The C API functions <code class="docutils literal notranslate">PyParser_SimpleParseStringFlags</code>,
<code class="docutils literal notranslate">PyParser_SimpleParseStringFlagsFilename</code>,
<code class="docutils literal notranslate">PyParser_SimpleParseFileFlags</code>, <code class="docutils literal notranslate">PyNode_Compile</code> and the type
used by these functions, <code class="docutils literal notranslate">struct _node</code>, were removed due to the switch
to the new PEG parser.
Source should be now be compiled directly to a code object using, for
example, <a class="reference internal" href="../c-api/veryhigh.html#c.Py_CompileString" title="Py_CompileString"><code class="xref c c-func docutils literal notranslate">Py_CompileString()</code></a>. The resulting code object can then be
evaluated using, for example, <a class="reference internal" href="../c-api/veryhigh.html#c.PyEval_EvalCode" title="PyEval_EvalCode"><code class="xref c c-func docutils literal notranslate">PyEval_EvalCode()</code></a>.
Specifically:
<ul>
<li>A call to <code class="docutils literal notranslate">PyParser_SimpleParseStringFlags</code> followed by
<code class="docutils literal notranslate">PyNode_Compile</code> can be replaced by calling <a class="reference internal" href="../c-api/veryhigh.html#c.Py_CompileString" title="Py_CompileString"><code class="xref c c-func docutils literal notranslate">Py_CompileString()</code></a>.</li>
<li>There is no direct replacement for <code class="docutils literal notranslate">PyParser_SimpleParseFileFlags</code>.
To compile code from a <code class="docutils literal notranslate">FILE *</code> argument, you will need to read
the file in C and pass the resulting buffer to <a class="reference internal" href="../c-api/veryhigh.html#c.Py_CompileString" title="Py_CompileString"><code class="xref c c-func docutils literal notranslate">Py_CompileString()</code></a>.</li>
<li>To compile a file given a <code class="docutils literal notranslate">char *</code> filename, explicitly open the file, read
it and compile the result. One way to do this is using the <a class="reference internal" href="../library/io.html#module-io" title="io: Core tools for working with streams."><code class="xref py py-mod docutils literal notranslate">io</code></a>
module with <a class="reference internal" href="../c-api/import.html#c.PyImport_ImportModule" title="PyImport_ImportModule"><code class="xref c c-func docutils literal notranslate">PyImport_ImportModule()</code></a>, <a class="reference internal" href="../c-api/call.html#c.PyObject_CallMethod" title="PyObject_CallMethod"><code class="xref c c-func docutils literal notranslate">PyObject_CallMethod()</code></a>,
<a class="reference internal" href="../c-api/bytes.html#c.PyBytes_AsString" title="PyBytes_AsString"><code class="xref c c-func docutils literal notranslate">PyBytes_AsString()</code></a> and <a class="reference internal" href="../c-api/veryhigh.html#c.Py_CompileString" title="Py_CompileString"><code class="xref c c-func docutils literal notranslate">Py_CompileString()</code></a>,
as sketched below. (Declarations and error handling are omitted.)
<div class="highlight-python3 notranslate"><div class="highlight"><pre>io_module = Import_ImportModule(&quot;io&quot;);
fileobject = PyObject_CallMethod(io_module, &quot;open&quot;, &quot;ss&quot;, filename, &quot;rb&quot;);
source_bytes_object = PyObject_CallMethod(fileobject, &quot;read&quot;, &quot;&quot;);
result = PyObject_CallMethod(fileobject, &quot;close&quot;, &quot;&quot;);
source_buf = PyBytes_AsString(source_bytes_object);
code = Py_CompileString(source_buf, filename, Py_file_input);
</pre></div>
</div>
</li>
<li>For <code class="docutils literal notranslate">FrameObject</code> objects, the <code class="docutils literal notranslate">f_lasti</code> member now represents a wordcode
offset instead of a simple offset into the bytecode string. This means that this
number needs to be multiplied by 2 to be used with APIs that expect a byte offset
instead (like <a class="reference internal" href="../c-api/code.html#c.PyCode_Addr2Line" title="PyCode_Addr2Line"><code class="xref c c-func docutils literal notranslate">PyCode_Addr2Line()</code></a> for example). Notice as well that the
<code class="docutils literal notranslate">f_lasti</code> member of <code class="docutils literal notranslate">FrameObject</code> objects is not considered stable: please
use <a class="reference internal" href="../c-api/reflection.html#c.PyFrame_GetLineNumber" title="PyFrame_GetLineNumber"><code class="xref c c-func docutils literal notranslate">PyFrame_GetLineNumber()</code></a> instead.</li>
</ul>
</li>
</ul>
</section>
</section>
<section id="cpython-bytecode-changes">
<h2>CPython bytecode changes<a class="headerlink" href="#cpython-bytecode-changes" title="Permalink to this headline">¶</a></h2>
<ul class="simple">
<li>The <code class="docutils literal notranslate">MAKE_FUNCTION</code> instruction now accepts either a dict or a tuple of
strings as the function’s annotations.
(Contributed by Yurii Karabas and Inada Naoki in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42202">bpo-42202</a>.)</li>
</ul>
</section>
<section id="build-changes">
<h2>Build Changes<a class="headerlink" href="#build-changes" title="Permalink to this headline">¶</a></h2>
<ul>
<li><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0644">PEP 644</a>: Python now requires OpenSSL 1.1.1 or newer. OpenSSL 1.0.2 is no
longer supported.
(Contributed by Christian Heimes in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43669">bpo-43669</a>.)</li>
<li>The C99 functions <code class="xref c c-func docutils literal notranslate">snprintf()</code> and <code class="xref c c-func docutils literal notranslate">vsnprintf()</code> are now required
to build Python.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=36020">bpo-36020</a>.)</li>
<li><a class="reference internal" href="../library/sqlite3.html#module-sqlite3" title="sqlite3: A DB-API 2.0 implementation using SQLite 3.x."><code class="xref py py-mod docutils literal notranslate">sqlite3</code></a> requires SQLite 3.7.15 or higher. (Contributed by Sergey Fedoseev
and Erlend E. Aasland in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=40744">bpo-40744</a> and <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=40810">bpo-40810</a>.)</li>
<li>The <a class="reference internal" href="../library/atexit.html#module-atexit" title="atexit: Register and execute cleanup functions."><code class="xref py py-mod docutils literal notranslate">atexit</code></a> module must now always be built as a built-in module.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42639">bpo-42639</a>.)</li>
<li>Add <a class="reference internal" href="../using/configure.html#cmdoption-disable-test-modules"><code class="xref std std-option docutils literal notranslate">--disable-test-modules</code></a> option to the <code class="docutils literal notranslate">configure</code> script:
don’t build nor install test modules.
(Contributed by Xavier de Gaye, Thomas Petazzoni and Peixing Xin in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=27640">bpo-27640</a>.)</li>
<li>Add <a class="reference internal" href="../using/configure.html#cmdoption-with-wheel-pkg-dir"><code class="xref std std-option docutils literal notranslate">--with-wheel-pkg-dir=PATH option</code></a>
to the <code class="docutils literal notranslate">./configure</code> script. If
specified, the <a class="reference internal" href="../library/ensurepip.html#module-ensurepip" title="ensurepip: Bootstrapping the &quot;pip&quot; installer into an existing Python installation or virtual environment."><code class="xref py py-mod docutils literal notranslate">ensurepip</code></a> module looks for <code class="docutils literal notranslate">setuptools</code> and <code class="docutils literal notranslate">pip</code>
wheel packages in this directory: if both are present, these wheel packages
are used instead of ensurepip bundled wheel packages.
Some Linux distribution packaging policies recommend against bundling
dependencies. For example, Fedora installs wheel packages in the
<code class="docutils literal notranslate">/usr/share/python-wheels/</code> directory and don’t install the
<code class="docutils literal notranslate">ensurepip._bundled</code> package.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42856">bpo-42856</a>.)
</li>
<li>Add a new <a class="reference internal" href="../using/configure.html#cmdoption-without-static-libpython"><code class="xref std std-option docutils literal notranslate">configure --without-static-libpython option</code></a> to not build the <code class="docutils literal notranslate">libpythonMAJOR.MINOR.a</code>
static library and not install the <code class="docutils literal notranslate">python.o</code> object file.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43103">bpo-43103</a>.)
</li>
<li>The <code class="docutils literal notranslate">configure</code> script now uses the <code class="docutils literal notranslate">pkg-config</code> utility, if available,
to detect the location of Tcl/Tk headers and libraries. As before, those
locations can be explicitly specified with the <a class="reference internal" href="../using/configure.html#cmdoption-with-tcltk-includes"><code class="xref std std-option docutils literal notranslate">--with-tcltk-includes</code></a>
and <a class="reference internal" href="../using/configure.html#cmdoption-with-tcltk-libs"><code class="xref std std-option docutils literal notranslate">--with-tcltk-libs</code></a> configuration options.
(Contributed by Manolis Stamatogiannakis in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42603">bpo-42603</a>.)</li>
<li>Add <a class="reference internal" href="../using/configure.html#cmdoption-with-openssl-rpath"><code class="xref std std-option docutils literal notranslate">--with-openssl-rpath</code></a> option to <code class="docutils literal notranslate">configure</code> script. The option
simplifies building Python with a custom OpenSSL installation, e.g.
<code class="docutils literal notranslate">./configure --with-openssl=/path/to/openssl --with-openssl-rpath=auto</code>.
(Contributed by Christian Heimes in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43466">bpo-43466</a>.)</li>
</ul>
</section>
<section id="c-api-changes">
<h2>C API Changes<a class="headerlink" href="#c-api-changes" title="Permalink to this headline">¶</a></h2>
<section id="pep-652-maintaining-the-stable-abi">
<h3>PEP 652: Maintaining the Stable ABI<a class="headerlink" href="#pep-652-maintaining-the-stable-abi" title="Permalink to this headline">¶</a></h3>
The Stable ABI (Application Binary Interface) for extension modules or
embedding Python is now explicitly defined.
<a class="reference internal" href="../c-api/stable.html#stable">C API Stability</a> describes C API and ABI stability guarantees along with best
practices for using the Stable ABI.
(Contributed by Petr Viktorin in <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0652">PEP 652</a> and <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43795">bpo-43795</a>.)
</section>
<section id="id1">
<h3>New Features<a class="headerlink" href="#id1" title="Permalink to this headline">¶</a></h3>
<ul>
<li>The result of <a class="reference internal" href="../c-api/number.html#c.PyNumber_Index" title="PyNumber_Index"><code class="xref c c-func docutils literal notranslate">PyNumber_Index()</code></a> now always has exact type <a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a>.
Previously, the result could have been an instance of a subclass of <code class="docutils literal notranslate">int</code>.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=40792">bpo-40792</a>.)</li>
<li>Add a new <a class="reference internal" href="../c-api/init_config.html#c.PyConfig.orig_argv" title="PyConfig.orig_argv"><code class="xref c c-member docutils literal notranslate">orig_argv</code></a> member to the <a class="reference internal" href="../c-api/init_config.html#c.PyConfig" title="PyConfig"><code class="xref c c-type docutils literal notranslate">PyConfig</code></a>
structure: the list of the original command line arguments passed to the
Python executable.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=23427">bpo-23427</a>.)</li>
<li>The <a class="reference internal" href="../c-api/datetime.html#c.PyDateTime_DATE_GET_TZINFO" title="PyDateTime_DATE_GET_TZINFO"><code class="xref c c-func docutils literal notranslate">PyDateTime_DATE_GET_TZINFO()</code></a> and
<a class="reference internal" href="../c-api/datetime.html#c.PyDateTime_TIME_GET_TZINFO" title="PyDateTime_TIME_GET_TZINFO"><code class="xref c c-func docutils literal notranslate">PyDateTime_TIME_GET_TZINFO()</code></a> macros have been added for accessing
the <code class="docutils literal notranslate">tzinfo</code> attributes of <a class="reference internal" href="../library/datetime.html#datetime.datetime" title="datetime.datetime"><code class="xref py py-class docutils literal notranslate">datetime.datetime</code></a> and
<a class="reference internal" href="../library/datetime.html#datetime.time" title="datetime.time"><code class="xref py py-class docutils literal notranslate">datetime.time</code></a> objects.
(Contributed by Zackery Spytz in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=30155">bpo-30155</a>.)</li>
<li>Add a <a class="reference internal" href="../c-api/codec.html#c.PyCodec_Unregister" title="PyCodec_Unregister"><code class="xref c c-func docutils literal notranslate">PyCodec_Unregister()</code></a> function to unregister a codec
search function.
(Contributed by Hai Shi in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41842">bpo-41842</a>.)</li>
<li>The <a class="reference internal" href="../c-api/iter.html#c.PyIter_Send" title="PyIter_Send"><code class="xref c c-func docutils literal notranslate">PyIter_Send()</code></a> function was added to allow
sending value into iterator without raising <code class="docutils literal notranslate">StopIteration</code> exception.
(Contributed by Vladimir Matveev in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41756">bpo-41756</a>.)</li>
<li>Add <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_AsUTF8AndSize" title="PyUnicode_AsUTF8AndSize"><code class="xref c c-func docutils literal notranslate">PyUnicode_AsUTF8AndSize()</code></a> to the limited C API.
(Contributed by Alex Gaynor in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41784">bpo-41784</a>.)</li>
<li>Add <a class="reference internal" href="../c-api/module.html#c.PyModule_AddObjectRef" title="PyModule_AddObjectRef"><code class="xref c c-func docutils literal notranslate">PyModule_AddObjectRef()</code></a> function: similar to
<a class="reference internal" href="../c-api/module.html#c.PyModule_AddObject" title="PyModule_AddObject"><code class="xref c c-func docutils literal notranslate">PyModule_AddObject()</code></a> but don’t steal a reference to the value on
success.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1635741">bpo-1635741</a>.)</li>
<li>Add <a class="reference internal" href="../c-api/refcounting.html#c.Py_NewRef" title="Py_NewRef"><code class="xref c c-func docutils literal notranslate">Py_NewRef()</code></a> and <a class="reference internal" href="../c-api/refcounting.html#c.Py_XNewRef" title="Py_XNewRef"><code class="xref c c-func docutils literal notranslate">Py_XNewRef()</code></a> functions to increment the
reference count of an object and return the object.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42262">bpo-42262</a>.)</li>
<li>The <a class="reference internal" href="../c-api/type.html#c.PyType_FromSpecWithBases" title="PyType_FromSpecWithBases"><code class="xref c c-func docutils literal notranslate">PyType_FromSpecWithBases()</code></a> and <a class="reference internal" href="../c-api/type.html#c.PyType_FromModuleAndSpec" title="PyType_FromModuleAndSpec"><code class="xref c c-func docutils literal notranslate">PyType_FromModuleAndSpec()</code></a>
functions now accept a single class as the bases argument.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42423">bpo-42423</a>.)</li>
<li>The <a class="reference internal" href="../c-api/type.html#c.PyType_FromModuleAndSpec" title="PyType_FromModuleAndSpec"><code class="xref c c-func docutils literal notranslate">PyType_FromModuleAndSpec()</code></a> function now accepts NULL <code class="docutils literal notranslate">tp_doc</code>
slot.
(Contributed by Hai Shi in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41832">bpo-41832</a>.)</li>
<li>The <a class="reference internal" href="../c-api/type.html#c.PyType_GetSlot" title="PyType_GetSlot"><code class="xref c c-func docutils literal notranslate">PyType_GetSlot()</code></a> function can accept
<a class="reference internal" href="../c-api/typeobj.html#static-types">static types</a>.
(Contributed by Hai Shi and Petr Viktorin in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41073">bpo-41073</a>.)</li>
<li>Add a new <a class="reference internal" href="../c-api/set.html#c.PySet_CheckExact" title="PySet_CheckExact"><code class="xref c c-func docutils literal notranslate">PySet_CheckExact()</code></a> function to the C-API to check if an
object is an instance of <a class="reference internal" href="../library/stdtypes.html#set" title="set"><code class="xref py py-class docutils literal notranslate">set</code></a> but not an instance of a subtype.
(Contributed by Pablo Galindo in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43277">bpo-43277</a>.)</li>
<li>Add <a class="reference internal" href="../c-api/exceptions.html#c.PyErr_SetInterruptEx" title="PyErr_SetInterruptEx"><code class="xref c c-func docutils literal notranslate">PyErr_SetInterruptEx()</code></a> which allows passing a signal number
to simulate.
(Contributed by Antoine Pitrou in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43356">bpo-43356</a>.)</li>
<li>The limited C API is now supported if <a class="reference internal" href="../using/configure.html#debug-build">Python is built in debug mode</a> (if the <code class="docutils literal notranslate">Py_DEBUG</code> macro is defined). In the limited C API,
the <a class="reference internal" href="../c-api/refcounting.html#c.Py_INCREF" title="Py_INCREF"><code class="xref c c-func docutils literal notranslate">Py_INCREF()</code></a> and <a class="reference internal" href="../c-api/refcounting.html#c.Py_DECREF" title="Py_DECREF"><code class="xref c c-func docutils literal notranslate">Py_DECREF()</code></a> functions are now implemented
as opaque function
calls, rather than accessing directly the <a class="reference internal" href="../c-api/typeobj.html#c.PyObject.ob_refcnt" title="PyObject.ob_refcnt"><code class="xref c c-member docutils literal notranslate">PyObject.ob_refcnt</code></a>
member, if Python is built in debug mode and the <code class="docutils literal notranslate">Py_LIMITED_API</code> macro
targets Python 3.10 or newer. It became possible to support the limited C API
in debug mode because the <a class="reference internal" href="../c-api/structures.html#c.PyObject" title="PyObject"><code class="xref c c-type docutils literal notranslate">PyObject</code></a> structure is the same in release
and debug mode since Python 3.8 (see <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=36465">bpo-36465</a>).
The limited C API is still not supported in the <a class="reference internal" href="../using/configure.html#cmdoption-with-trace-refs"><code class="xref std std-option docutils literal notranslate">--with-trace-refs</code></a>
special build (<code class="docutils literal notranslate">Py_TRACE_REFS</code> macro).
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43688">bpo-43688</a>.)
</li>
<li>Add the <a class="reference internal" href="../c-api/structures.html#c.Py_Is" title="Py_Is"><code class="xref c c-func docutils literal notranslate">Py_Is(x, y)</code></a> function to test if the x object is
the y object, the same as <code class="docutils literal notranslate">x is y</code> in Python. Add also the
<a class="reference internal" href="../c-api/structures.html#c.Py_IsNone" title="Py_IsNone"><code class="xref c c-func docutils literal notranslate">Py_IsNone()</code></a>, <a class="reference internal" href="../c-api/structures.html#c.Py_IsTrue" title="Py_IsTrue"><code class="xref c c-func docutils literal notranslate">Py_IsTrue()</code></a>, <a class="reference internal" href="../c-api/structures.html#c.Py_IsFalse" title="Py_IsFalse"><code class="xref c c-func docutils literal notranslate">Py_IsFalse()</code></a> functions to
test if an object is, respectively, the <code class="docutils literal notranslate">None</code> singleton, the <code class="docutils literal notranslate">True</code>
singleton or the <code class="docutils literal notranslate">False</code> singleton.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43753">bpo-43753</a>.)</li>
<li>Add new functions to control the garbage collector from C code:
<a class="reference internal" href="../c-api/gcsupport.html#c.PyGC_Enable" title="PyGC_Enable"><code class="xref c c-func docutils literal notranslate">PyGC_Enable()</code></a>,
<a class="reference internal" href="../c-api/gcsupport.html#c.PyGC_Disable" title="PyGC_Disable"><code class="xref c c-func docutils literal notranslate">PyGC_Disable()</code></a>,
<a class="reference internal" href="../c-api/gcsupport.html#c.PyGC_IsEnabled" title="PyGC_IsEnabled"><code class="xref c c-func docutils literal notranslate">PyGC_IsEnabled()</code></a>.
These functions allow to activate, deactivate and query the state of the garbage collector from C code without
having to import the <a class="reference internal" href="../library/gc.html#module-gc" title="gc: Interface to the cycle-detecting garbage collector."><code class="xref py py-mod docutils literal notranslate">gc</code></a> module.</li>
<li>Add a new <code class="xref c c-data docutils literal notranslate">Py_TPFLAGS_DISALLOW_INSTANTIATION</code> type flag to disallow
creating type instances.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43916">bpo-43916</a>.)</li>
<li>Add a new <code class="xref c c-data docutils literal notranslate">Py_TPFLAGS_IMMUTABLETYPE</code> type flag for creating immutable
type objects: type attributes cannot be set nor deleted.
(Contributed by Victor Stinner and Erlend E. Aasland in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43908">bpo-43908</a>.)</li>
</ul>
</section>
<section id="id2">
<h3>Porting to Python 3.10<a class="headerlink" href="#id2" title="Permalink to this headline">¶</a></h3>
<ul>
<li>The <code class="docutils literal notranslate">PY_SSIZE_T_CLEAN</code> macro must now be defined to use
<a class="reference internal" href="../c-api/arg.html#c.PyArg_ParseTuple" title="PyArg_ParseTuple"><code class="xref c c-func docutils literal notranslate">PyArg_ParseTuple()</code></a> and <a class="reference internal" href="../c-api/arg.html#c.Py_BuildValue" title="Py_BuildValue"><code class="xref c c-func docutils literal notranslate">Py_BuildValue()</code></a> formats which use
<code class="docutils literal notranslate">#</code>: <code class="docutils literal notranslate">es#</code>, <code class="docutils literal notranslate">et#</code>, <code class="docutils literal notranslate">s#</code>, <code class="docutils literal notranslate">u#</code>, <code class="docutils literal notranslate">y#</code>, <code class="docutils literal notranslate">z#</code>, <code class="docutils literal notranslate">U#</code> and <code class="docutils literal notranslate">Z#</code>.
See <a class="reference internal" href="../c-api/arg.html#arg-parsing">Parsing arguments and building values</a> and <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0353">PEP 353</a>.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=40943">bpo-40943</a>.)</li>
<li>Since <a class="reference internal" href="../c-api/structures.html#c.Py_REFCNT" title="Py_REFCNT"><code class="xref c c-func docutils literal notranslate">Py_REFCNT()</code></a> is changed to the inline static function,
<code class="docutils literal notranslate">Py_REFCNT(obj) = new_refcnt</code> must be replaced with <code class="docutils literal notranslate">Py_SET_REFCNT(obj, new_refcnt)</code>:
see <a class="reference internal" href="../c-api/structures.html#c.Py_SET_REFCNT" title="Py_SET_REFCNT"><code class="xref c c-func docutils literal notranslate">Py_SET_REFCNT()</code></a> (available since Python 3.9). For backward
compatibility, this macro can be used:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>#if PY_VERSION_HEX &lt; 0x030900A4
# define Py_SET_REFCNT(obj, refcnt) ((Py_REFCNT(obj) = (refcnt)), (void)0)
#endif
</pre></div>
</div>
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=39573">bpo-39573</a>.)
</li>
<li>Calling <a class="reference internal" href="../c-api/dict.html#c.PyDict_GetItem" title="PyDict_GetItem"><code class="xref c c-func docutils literal notranslate">PyDict_GetItem()</code></a> without <a class="reference internal" href="../glossary.html#term-GIL">GIL</a> held had been allowed
for historical reason. It is no longer allowed.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=40839">bpo-40839</a>.)</li>
<li><code class="docutils literal notranslate">PyUnicode_FromUnicode(NULL, size)</code> and <code class="docutils literal notranslate">PyUnicode_FromStringAndSize(NULL, size)</code>
raise <code class="docutils literal notranslate">DeprecationWarning</code> now. Use <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_New" title="PyUnicode_New"><code class="xref c c-func docutils literal notranslate">PyUnicode_New()</code></a> to allocate
Unicode object without initial data.
(Contributed by Inada Naoki in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=36346">bpo-36346</a>.)</li>
<li>The private <code class="docutils literal notranslate">_PyUnicode_Name_CAPI</code> structure of the PyCapsule API
<code class="docutils literal notranslate">unicodedata.ucnhash_CAPI</code> has been moved to the internal C API.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42157">bpo-42157</a>.)</li>
<li><a class="reference internal" href="../c-api/init.html#c.Py_GetPath" title="Py_GetPath"><code class="xref c c-func docutils literal notranslate">Py_GetPath()</code></a>, <a class="reference internal" href="../c-api/init.html#c.Py_GetPrefix" title="Py_GetPrefix"><code class="xref c c-func docutils literal notranslate">Py_GetPrefix()</code></a>, <a class="reference internal" href="../c-api/init.html#c.Py_GetExecPrefix" title="Py_GetExecPrefix"><code class="xref c c-func docutils literal notranslate">Py_GetExecPrefix()</code></a>,
<a class="reference internal" href="../c-api/init.html#c.Py_GetProgramFullPath" title="Py_GetProgramFullPath"><code class="xref c c-func docutils literal notranslate">Py_GetProgramFullPath()</code></a>, <a class="reference internal" href="../c-api/init.html#c.Py_GetPythonHome" title="Py_GetPythonHome"><code class="xref c c-func docutils literal notranslate">Py_GetPythonHome()</code></a> and
<a class="reference internal" href="../c-api/init.html#c.Py_GetProgramName" title="Py_GetProgramName"><code class="xref c c-func docutils literal notranslate">Py_GetProgramName()</code></a> functions now return <code class="docutils literal notranslate">NULL</code> if called before
<a class="reference internal" href="../c-api/init.html#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate">Py_Initialize()</code></a> (before Python is initialized). Use the new
<a class="reference internal" href="../c-api/init_config.html#init-config">Python Initialization Configuration</a> API to get the <a class="reference internal" href="../c-api/init_config.html#init-path-config">Python Path Configuration</a>.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=42260">bpo-42260</a>.)</li>
<li><a class="reference internal" href="../c-api/list.html#c.PyList_SET_ITEM" title="PyList_SET_ITEM"><code class="xref c c-func docutils literal notranslate">PyList_SET_ITEM()</code></a>, <a class="reference internal" href="../c-api/tuple.html#c.PyTuple_SET_ITEM" title="PyTuple_SET_ITEM"><code class="xref c c-func docutils literal notranslate">PyTuple_SET_ITEM()</code></a> and
<a class="reference internal" href="../c-api/cell.html#c.PyCell_SET" title="PyCell_SET"><code class="xref c c-func docutils literal notranslate">PyCell_SET()</code></a> macros can no longer be used as l-value or r-value.
For example, <code class="docutils literal notranslate">x = PyList_SET_ITEM(a, b, c)</code> and
<code class="docutils literal notranslate">PyList_SET_ITEM(a, b, c) = x</code> now fail with a compiler error. It prevents
bugs like <code class="docutils literal notranslate">if (PyList_SET_ITEM (a, b, c) &lt; 0) ...</code> test.
(Contributed by Zackery Spytz and Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=30459">bpo-30459</a>.)</li>
<li>The non-limited API files <code class="docutils literal notranslate">odictobject.h</code>, <code class="docutils literal notranslate">parser_interface.h</code>,
<code class="docutils literal notranslate">picklebufobject.h</code>, <code class="docutils literal notranslate">pyarena.h</code>, <code class="docutils literal notranslate">pyctype.h</code>, <code class="docutils literal notranslate">pydebug.h</code>,
<code class="docutils literal notranslate">pyfpe.h</code>, and <code class="docutils literal notranslate">pytime.h</code> have been moved to the <code class="docutils literal notranslate">Include/cpython</code>
directory. These files must not be included directly, as they are already
included in <code class="docutils literal notranslate">Python.h</code>; see <a class="reference internal" href="../c-api/intro.html#api-includes">Include Files</a>. If they have
been included directly, consider including <code class="docutils literal notranslate">Python.h</code> instead.
(Contributed by Nicholas Sim in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=35134">bpo-35134</a>.)</li>
<li>Use the <code class="xref c c-data docutils literal notranslate">Py_TPFLAGS_IMMUTABLETYPE</code> type flag to create immutable type
objects. Do not rely on <code class="xref c c-data docutils literal notranslate">Py_TPFLAGS_HEAPTYPE</code> to decide if a type
object is mutable or not; check if <code class="xref c c-data docutils literal notranslate">Py_TPFLAGS_IMMUTABLETYPE</code> is set
instead.
(Contributed by Victor Stinner and Erlend E. Aasland in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43908">bpo-43908</a>.)</li>
<li>The undocumented function <code class="docutils literal notranslate">Py_FrozenMain</code> has been removed from the
limited API. The function is mainly useful for custom builds of Python.
(Contributed by Petr Viktorin in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=26241">bpo-26241</a>.)</li>
</ul>
</section>
<section id="id3">
<h3>Deprecated<a class="headerlink" href="#id3" title="Permalink to this headline">¶</a></h3>
<ul class="simple">
<li>The <code class="docutils literal notranslate">PyUnicode_InternImmortal()</code> function is now deprecated
and will be removed in Python 3.12: use <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_InternInPlace" title="PyUnicode_InternInPlace"><code class="xref c c-func docutils literal notranslate">PyUnicode_InternInPlace()</code></a>
instead.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41692">bpo-41692</a>.)</li>
</ul>
</section>
<section id="id4">
<h3>Removed<a class="headerlink" href="#id4" title="Permalink to this headline">¶</a></h3>
<ul>
<li>Removed <code class="docutils literal notranslate">Py_UNICODE_str*</code> functions manipulating <code class="docutils literal notranslate">Py_UNICODE*</code> strings.
(Contributed by Inada Naoki in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41123">bpo-41123</a>.)
<blockquote>
<div><ul class="simple">
<li><code class="docutils literal notranslate">Py_UNICODE_strlen</code>: use <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_GetLength" title="PyUnicode_GetLength"><code class="xref c c-func docutils literal notranslate">PyUnicode_GetLength()</code></a> or
<a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_GET_LENGTH" title="PyUnicode_GET_LENGTH"><code class="xref c c-macro docutils literal notranslate">PyUnicode_GET_LENGTH</code></a></li>
<li><code class="docutils literal notranslate">Py_UNICODE_strcat</code>: use <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_CopyCharacters" title="PyUnicode_CopyCharacters"><code class="xref c c-func docutils literal notranslate">PyUnicode_CopyCharacters()</code></a> or
<a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_FromFormat" title="PyUnicode_FromFormat"><code class="xref c c-func docutils literal notranslate">PyUnicode_FromFormat()</code></a></li>
<li><code class="docutils literal notranslate">Py_UNICODE_strcpy</code>, <code class="docutils literal notranslate">Py_UNICODE_strncpy</code>: use
<a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_CopyCharacters" title="PyUnicode_CopyCharacters"><code class="xref c c-func docutils literal notranslate">PyUnicode_CopyCharacters()</code></a> or <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_Substring" title="PyUnicode_Substring"><code class="xref c c-func docutils literal notranslate">PyUnicode_Substring()</code></a></li>
<li><code class="docutils literal notranslate">Py_UNICODE_strcmp</code>: use <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_Compare" title="PyUnicode_Compare"><code class="xref c c-func docutils literal notranslate">PyUnicode_Compare()</code></a></li>
<li><code class="docutils literal notranslate">Py_UNICODE_strncmp</code>: use <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_Tailmatch" title="PyUnicode_Tailmatch"><code class="xref c c-func docutils literal notranslate">PyUnicode_Tailmatch()</code></a></li>
<li><code class="docutils literal notranslate">Py_UNICODE_strchr</code>, <code class="docutils literal notranslate">Py_UNICODE_strrchr</code>: use
<a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_FindChar" title="PyUnicode_FindChar"><code class="xref c c-func docutils literal notranslate">PyUnicode_FindChar()</code></a></li>
</ul>
</div></blockquote>
</li>
<li>Removed <code class="docutils literal notranslate">PyUnicode_GetMax()</code>. Please migrate to new (<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0393">PEP 393</a>) APIs.
(Contributed by Inada Naoki in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41103">bpo-41103</a>.)</li>
<li>Removed <code class="docutils literal notranslate">PyLong_FromUnicode()</code>. Please migrate to <a class="reference internal" href="../c-api/long.html#c.PyLong_FromUnicodeObject" title="PyLong_FromUnicodeObject"><code class="xref c c-func docutils literal notranslate">PyLong_FromUnicodeObject()</code></a>.
(Contributed by Inada Naoki in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41103">bpo-41103</a>.)</li>
<li>Removed <code class="docutils literal notranslate">PyUnicode_AsUnicodeCopy()</code>. Please use <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_AsUCS4Copy" title="PyUnicode_AsUCS4Copy"><code class="xref c c-func docutils literal notranslate">PyUnicode_AsUCS4Copy()</code></a> or
<a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_AsWideCharString" title="PyUnicode_AsWideCharString"><code class="xref c c-func docutils literal notranslate">PyUnicode_AsWideCharString()</code></a>
(Contributed by Inada Naoki in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41103">bpo-41103</a>.)</li>
<li>Removed <code class="docutils literal notranslate">_Py_CheckRecursionLimit</code> variable: it has been replaced by
<code class="docutils literal notranslate">ceval.recursion_limit</code> of the <a class="reference internal" href="../c-api/init.html#c.PyInterpreterState" title="PyInterpreterState"><code class="xref c c-type docutils literal notranslate">PyInterpreterState</code></a> structure.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41834">bpo-41834</a>.)</li>
<li>Removed undocumented macros <code class="docutils literal notranslate">Py_ALLOW_RECURSION</code> and
<code class="docutils literal notranslate">Py_END_ALLOW_RECURSION</code> and the <code class="docutils literal notranslate">recursion_critical</code> field of the
<a class="reference internal" href="../c-api/init.html#c.PyInterpreterState" title="PyInterpreterState"><code class="xref c c-type docutils literal notranslate">PyInterpreterState</code></a> structure.
(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41936">bpo-41936</a>.)</li>
<li>Removed the undocumented <code class="docutils literal notranslate">PyOS_InitInterrupts()</code> function. Initializing
Python already implicitly installs signal handlers: see
<a class="reference internal" href="../c-api/init_config.html#c.PyConfig.install_signal_handlers" title="PyConfig.install_signal_handlers"><code class="xref c c-member docutils literal notranslate">PyConfig.install_signal_handlers</code></a>.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=41713">bpo-41713</a>.)</li>
<li>Remove the <code class="docutils literal notranslate">PyAST_Validate()</code> function. It is no longer possible to build a
AST object (<code class="docutils literal notranslate">mod_ty</code> type) with the public C API. The function was already
excluded from the limited C API (<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0384">PEP 384</a>).
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43244">bpo-43244</a>.)</li>
<li>Remove the <code class="docutils literal notranslate">symtable.h</code> header file and the undocumented functions:
<ul class="simple">
<li><code class="docutils literal notranslate">PyST_GetScope()</code></li>
<li><code class="docutils literal notranslate">PySymtable_Build()</code></li>
<li><code class="docutils literal notranslate">PySymtable_BuildObject()</code></li>
<li><code class="docutils literal notranslate">PySymtable_Free()</code></li>
<li><code class="docutils literal notranslate">Py_SymtableString()</code></li>
<li><code class="docutils literal notranslate">Py_SymtableStringObject()</code></li>
</ul>
The <code class="docutils literal notranslate">Py_SymtableString()</code> function was part the stable ABI by mistake but
it could not be used, because the <code class="docutils literal notranslate">symtable.h</code> header file was excluded
from the limited C API.
Use Python <a class="reference internal" href="../library/symtable.html#module-symtable" title="symtable: Interface to the compiler's internal symbol tables."><code class="xref py py-mod docutils literal notranslate">symtable</code></a> module instead.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43244">bpo-43244</a>.)
</li>
<li>Remove <a class="reference internal" href="../c-api/veryhigh.html#c.PyOS_ReadlineFunctionPointer" title="PyOS_ReadlineFunctionPointer"><code class="xref c c-func docutils literal notranslate">PyOS_ReadlineFunctionPointer()</code></a> from the limited C API headers
and from <code class="docutils literal notranslate">python3.dll</code>, the library that provides the stable ABI on
Windows. Since the function takes a <code class="docutils literal notranslate">FILE*</code> argument, its ABI stability
cannot be guaranteed.
(Contributed by Petr Viktorin in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43868">bpo-43868</a>.)</li>
<li>Remove <code class="docutils literal notranslate">ast.h</code>, <code class="docutils literal notranslate">asdl.h</code>, and <code class="docutils literal notranslate">Python-ast.h</code> header files.
These functions were undocumented and excluded from the limited C API.
Most names defined by these header files were not prefixed by <code class="docutils literal notranslate">Py</code> and so
could create names conflicts. For example, <code class="docutils literal notranslate">Python-ast.h</code> defined a
<code class="docutils literal notranslate">Yield</code> macro which was conflict with the <code class="docutils literal notranslate">Yield</code> name used by the
Windows <code class="docutils literal notranslate">&lt;winbase.h&gt;</code> header. Use the Python <a class="reference internal" href="../library/ast.html#module-ast" title="ast: Abstract Syntax Tree classes and manipulation."><code class="xref py py-mod docutils literal notranslate">ast</code></a> module instead.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43244">bpo-43244</a>.)</li>
<li>Remove the compiler and parser functions using <code class="docutils literal notranslate">struct _mod</code> type, because
the public AST C API was removed:
<ul class="simple">
<li><code class="docutils literal notranslate">PyAST_Compile()</code></li>
<li><code class="docutils literal notranslate">PyAST_CompileEx()</code></li>
<li><code class="docutils literal notranslate">PyAST_CompileObject()</code></li>
<li><code class="docutils literal notranslate">PyFuture_FromAST()</code></li>
<li><code class="docutils literal notranslate">PyFuture_FromASTObject()</code></li>
<li><code class="docutils literal notranslate">PyParser_ASTFromFile()</code></li>
<li><code class="docutils literal notranslate">PyParser_ASTFromFileObject()</code></li>
<li><code class="docutils literal notranslate">PyParser_ASTFromFilename()</code></li>
<li><code class="docutils literal notranslate">PyParser_ASTFromString()</code></li>
<li><code class="docutils literal notranslate">PyParser_ASTFromStringObject()</code></li>
</ul>
These functions were undocumented and excluded from the limited C API.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43244">bpo-43244</a>.)
</li>
<li>Remove the <code class="docutils literal notranslate">pyarena.h</code> header file with functions:
<ul class="simple">
<li><code class="docutils literal notranslate">PyArena_New()</code></li>
<li><code class="docutils literal notranslate">PyArena_Free()</code></li>
<li><code class="docutils literal notranslate">PyArena_Malloc()</code></li>
<li><code class="docutils literal notranslate">PyArena_AddPyObject()</code></li>
</ul>
These functions were undocumented, excluded from the limited C API, and were
only used internally by the compiler.
(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43244">bpo-43244</a>.)
</li>
<li>The <code class="docutils literal notranslate">PyThreadState.use_tracing</code> member has been removed to optimize Python.
(Contributed by Mark Shannon in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=43760">bpo-43760</a>.)</li>
</ul>
</section>
</section>
<section id="notable-security-feature-in-3-10-7">
<h2>Notable security feature in 3.10.7<a class="headerlink" href="#notable-security-feature-in-3-10-7" title="Permalink to this headline">¶</a></h2>
Converting between <a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a> and <a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> in bases other than 2
(binary), 4, 8 (octal), 16 (hexadecimal), or 32 such as base 10 (decimal)
now raises a <a class="reference internal" href="../library/exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate">ValueError</code></a> if the number of digits in string form is
above a limit to avoid potential denial of service attacks due to the
algorithmic complexity. This is a mitigation for <a class="reference external" href="https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-10735">CVE-2020-10735</a>.
This limit can be configured or disabled by environment variable, command
line flag, or <a class="reference internal" href="../library/sys.html#module-sys" title="sys: Access system-specific parameters and functions."><code class="xref py py-mod docutils literal notranslate">sys</code></a> APIs. See the <a class="reference internal" href="../library/stdtypes.html#int-max-str-digits">integer string conversion
length limitation</a> documentation. The default limit
is 4300 digits in string form.
</section>
<section id="notable-security-feature-in-3-10-8">
<h2>Notable security feature in 3.10.8<a class="headerlink" href="#notable-security-feature-in-3-10-8" title="Permalink to this headline">¶</a></h2>
The deprecated <a class="reference internal" href="../library/mailcap.html#module-mailcap" title="mailcap: Mailcap file handling. (deprecated)"><code class="xref py py-mod docutils literal notranslate">mailcap</code></a> module now refuses to inject unsafe text
(filenames, MIME types, parameters) into shell commands. Instead of using such
text, it will warn and act as if a match was not found (or for test commands,
as if the test failed).
(Contributed by Petr Viktorin in <a class="reference external" href="https://github.com/python/cpython/issues/98966">gh-98966</a>.)
</section>
<section id="notable-changes-in-3-10-12">
<h2>Notable Changes in 3.10.12<a class="headerlink" href="#notable-changes-in-3-10-12" title="Permalink to this headline">¶</a></h2>
<section id="tarfile">
<h3>tarfile<a class="headerlink" href="#tarfile" title="Permalink to this headline">¶</a></h3>
<ul class="simple">
<li>The extraction methods in <a class="reference internal" href="../library/tarfile.html#module-tarfile" title="tarfile: Read and write tar-format archive files."><code class="xref py py-mod docutils literal notranslate">tarfile</code></a>, and <a class="reference internal" href="../library/shutil.html#shutil.unpack_archive" title="shutil.unpack_archive"><code class="xref py py-func docutils literal notranslate">shutil.unpack_archive()</code></a>,
have a new a filter argument that allows limiting tar features than may be
surprising or dangerous, such as creating files outside the destination
directory.
See <a class="reference internal" href="../library/tarfile.html#tarfile-extraction-filter">Extraction filters</a> for details.
In Python 3.12, use without the filter argument will show a
<a class="reference internal" href="../library/exceptions.html#DeprecationWarning" title="DeprecationWarning"><code class="xref py py-exc docutils literal notranslate">DeprecationWarning</code></a>.
In Python 3.14, the default will switch to <code class="docutils literal notranslate">'data'</code>.
(Contributed by Petr Viktorin in <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0706">PEP 706</a>.)</li>
</ul>
</section>
</section>
</section>

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 </div>
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 <div class="sphinxsidebar" role="navigation" aria-label="main navigation">
 <div class="sphinxsidebarwrapper">
 <h3><a href="../contents.html">Table of Contents</a></h3>
 <ul>
<li><a class="reference internal" href="#">What’s New In Python 3.10</a><ul>
<li><a class="reference internal" href="#summary-release-highlights">Summary – Release highlights</a></li>
<li><a class="reference internal" href="#new-features">New Features</a><ul>
<li><a class="reference internal" href="#parenthesized-context-managers">Parenthesized context managers</a></li>
<li><a class="reference internal" href="#better-error-messages">Better error messages</a><ul>
<li><a class="reference internal" href="#syntaxerrors">SyntaxErrors</a></li>
<li><a class="reference internal" href="#indentationerrors">IndentationErrors</a></li>
<li><a class="reference internal" href="#attributeerrors">AttributeErrors</a></li>
<li><a class="reference internal" href="#nameerrors">NameErrors</a></li>
</ul>
</li>
<li><a class="reference internal" href="#pep-626-precise-line-numbers-for-debugging-and-other-tools">PEP 626: Precise line numbers for debugging and other tools</a></li>
<li><a class="reference internal" href="#pep-634-structural-pattern-matching">PEP 634: Structural Pattern Matching</a><ul>
<li><a class="reference internal" href="#syntax-and-operations">Syntax and operations</a></li>
<li><a class="reference internal" href="#declarative-approach">Declarative approach</a></li>
<li><a class="reference internal" href="#simple-pattern-match-to-a-literal">Simple pattern: match to a literal</a><ul>
<li><a class="reference internal" href="#behavior-without-the-wildcard">Behavior without the wildcard</a></li>
</ul>
</li>
<li><a class="reference internal" href="#patterns-with-a-literal-and-variable">Patterns with a literal and variable</a></li>
<li><a class="reference internal" href="#patterns-and-classes">Patterns and classes</a><ul>
<li><a class="reference internal" href="#patterns-with-positional-parameters">Patterns with positional parameters</a></li>
</ul>
</li>
<li><a class="reference internal" href="#nested-patterns">Nested patterns</a></li>
<li><a class="reference internal" href="#complex-patterns-and-the-wildcard">Complex patterns and the wildcard</a></li>
<li><a class="reference internal" href="#guard">Guard</a></li>
<li><a class="reference internal" href="#other-key-features">Other Key Features</a></li>
</ul>
</li>
<li><a class="reference internal" href="#optional-encodingwarning-and-encoding-locale-option">Optional <code class="docutils literal notranslate">EncodingWarning</code> and <code class="docutils literal notranslate">encoding=&quot;locale&quot;</code> option</a></li>
</ul>
</li>
<li><a class="reference internal" href="#new-features-related-to-type-hints">New Features Related to Type Hints</a><ul>
<li><a class="reference internal" href="#pep-604-new-type-union-operator">PEP 604: New Type Union Operator</a></li>
<li><a class="reference internal" href="#pep-612-parameter-specification-variables">PEP 612: Parameter Specification Variables</a></li>
<li><a class="reference internal" href="#pep-613-typealias">PEP 613: TypeAlias</a></li>
<li><a class="reference internal" href="#pep-647-user-defined-type-guards">PEP 647: User-Defined Type Guards</a></li>
</ul>
</li>
<li><a class="reference internal" href="#other-language-changes">Other Language Changes</a></li>
<li><a class="reference internal" href="#new-modules">New Modules</a></li>
<li><a class="reference internal" href="#improved-modules">Improved Modules</a><ul>
<li><a class="reference internal" href="#asyncio">asyncio</a></li>
<li><a class="reference internal" href="#argparse">argparse</a></li>
<li><a class="reference internal" href="#array">array</a></li>
<li><a class="reference internal" href="#asynchat-asyncore-smtpd">asynchat, asyncore, smtpd</a></li>
<li><a class="reference internal" href="#base64">base64</a></li>
<li><a class="reference internal" href="#bdb">bdb</a></li>
<li><a class="reference internal" href="#bisect">bisect</a></li>
<li><a class="reference internal" href="#codecs">codecs</a></li>
<li><a class="reference internal" href="#collections-abc">collections.abc</a></li>
<li><a class="reference internal" href="#contextlib">contextlib</a></li>
<li><a class="reference internal" href="#curses">curses</a></li>
<li><a class="reference internal" href="#dataclasses">dataclasses</a><ul>
<li><a class="reference internal" href="#slots">__slots__</a></li>
<li><a class="reference internal" href="#keyword-only-fields">Keyword-only fields</a></li>
</ul>
</li>
<li><a class="reference internal" href="#distutils">distutils</a></li>
<li><a class="reference internal" href="#doctest">doctest</a></li>
<li><a class="reference internal" href="#encodings">encodings</a></li>
<li><a class="reference internal" href="#fileinput">fileinput</a></li>
<li><a class="reference internal" href="#faulthandler">faulthandler</a></li>
<li><a class="reference internal" href="#gc">gc</a></li>
<li><a class="reference internal" href="#glob">glob</a></li>
<li><a class="reference internal" href="#hashlib">hashlib</a></li>
<li><a class="reference internal" href="#hmac">hmac</a></li>
<li><a class="reference internal" href="#idle-and-idlelib">IDLE and idlelib</a></li>
<li><a class="reference internal" href="#importlib-metadata">importlib.metadata</a></li>
<li><a class="reference internal" href="#inspect">inspect</a></li>
<li><a class="reference internal" href="#itertools">itertools</a></li>
<li><a class="reference internal" href="#linecache">linecache</a></li>
<li><a class="reference internal" href="#os">os</a></li>
<li><a class="reference internal" href="#os-path">os.path</a></li>
<li><a class="reference internal" href="#pathlib">pathlib</a></li>
<li><a class="reference internal" href="#platform">platform</a></li>
<li><a class="reference internal" href="#pprint">pprint</a></li>
<li><a class="reference internal" href="#py-compile">py_compile</a></li>
<li><a class="reference internal" href="#pyclbr">pyclbr</a></li>
<li><a class="reference internal" href="#shelve">shelve</a></li>
<li><a class="reference internal" href="#statistics">statistics</a></li>
<li><a class="reference internal" href="#site">site</a></li>
<li><a class="reference internal" href="#socket">socket</a></li>
<li><a class="reference internal" href="#ssl">ssl</a></li>
<li><a class="reference internal" href="#sqlite3">sqlite3</a></li>
<li><a class="reference internal" href="#sys">sys</a></li>
<li><a class="reference internal" href="#thread">_thread</a></li>
<li><a class="reference internal" href="#threading">threading</a></li>
<li><a class="reference internal" href="#traceback">traceback</a></li>
<li><a class="reference internal" href="#types">types</a></li>
<li><a class="reference internal" href="#typing">typing</a></li>
<li><a class="reference internal" href="#unittest">unittest</a></li>
<li><a class="reference internal" href="#urllib-parse">urllib.parse</a></li>
<li><a class="reference internal" href="#xml">xml</a></li>
<li><a class="reference internal" href="#zipimport">zipimport</a></li>
</ul>
</li>
<li><a class="reference internal" href="#optimizations">Optimizations</a></li>
<li><a class="reference internal" href="#deprecated">Deprecated</a></li>
<li><a class="reference internal" href="#removed">Removed</a></li>
<li><a class="reference internal" href="#porting-to-python-3-10">Porting to Python 3.10</a><ul>
<li><a class="reference internal" href="#changes-in-the-python-syntax">Changes in the Python syntax</a></li>
<li><a class="reference internal" href="#changes-in-the-python-api">Changes in the Python API</a></li>
<li><a class="reference internal" href="#changes-in-the-c-api">Changes in the C API</a></li>
</ul>
</li>
<li><a class="reference internal" href="#cpython-bytecode-changes">CPython bytecode changes</a></li>
<li><a class="reference internal" href="#build-changes">Build Changes</a></li>
<li><a class="reference internal" href="#c-api-changes">C API Changes</a><ul>
<li><a class="reference internal" href="#pep-652-maintaining-the-stable-abi">PEP 652: Maintaining the Stable ABI</a></li>
<li><a class="reference internal" href="#id1">New Features</a></li>
<li><a class="reference internal" href="#id2">Porting to Python 3.10</a></li>
<li><a class="reference internal" href="#id3">Deprecated</a></li>
<li><a class="reference internal" href="#id4">Removed</a></li>
</ul>
</li>
<li><a class="reference internal" href="#notable-security-feature-in-3-10-7">Notable security feature in 3.10.7</a></li>
<li><a class="reference internal" href="#notable-security-feature-in-3-10-8">Notable security feature in 3.10.8</a></li>
<li><a class="reference internal" href="#notable-changes-in-3-10-12">Notable Changes in 3.10.12</a><ul>
<li><a class="reference internal" href="#tarfile">tarfile</a></li>
</ul>
</li>
</ul>
</li>
</ul>

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