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 <h3><a href="../contents.html">Table of Contents</a></h3>
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<li><a class="reference internal" href="#"><code class="xref py py-mod docutils literal notranslate">typing</code> — Support for type hints</a><ul>
<li><a class="reference internal" href="#relevant-peps">Relevant PEPs</a></li>
<li><a class="reference internal" href="#type-aliases">Type aliases</a></li>
<li><a class="reference internal" href="#newtype">NewType</a></li>
<li><a class="reference internal" href="#callable">Callable</a></li>
<li><a class="reference internal" href="#generics">Generics</a></li>
<li><a class="reference internal" href="#user-defined-generic-types">User-defined generic types</a></li>
<li><a class="reference internal" href="#the-any-type">The <code class="xref py py-data docutils literal notranslate">Any</code> type</a></li>
<li><a class="reference internal" href="#nominal-vs-structural-subtyping">Nominal vs structural subtyping</a></li>
<li><a class="reference internal" href="#module-contents">Module contents</a><ul>
<li><a class="reference internal" href="#special-typing-primitives">Special typing primitives</a><ul>
<li><a class="reference internal" href="#special-types">Special types</a></li>
<li><a class="reference internal" href="#special-forms">Special forms</a></li>
<li><a class="reference internal" href="#building-generic-types">Building generic types</a></li>
<li><a class="reference internal" href="#other-special-directives">Other special directives</a></li>
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<li><a class="reference internal" href="#generic-concrete-collections">Generic concrete collections</a><ul>
<li><a class="reference internal" href="#corresponding-to-built-in-types">Corresponding to built-in types</a></li>
<li><a class="reference internal" href="#corresponding-to-types-in-collections">Corresponding to types in <code class="xref py py-mod docutils literal notranslate">collections</code></a></li>
<li><a class="reference internal" href="#other-concrete-types">Other concrete types</a></li>
</ul>
</li>
<li><a class="reference internal" href="#abstract-base-classes">Abstract Base Classes</a><ul>
<li><a class="reference internal" href="#corresponding-to-collections-in-collections-abc">Corresponding to collections in <code class="xref py py-mod docutils literal notranslate">collections.abc</code></a></li>
<li><a class="reference internal" href="#corresponding-to-other-types-in-collections-abc">Corresponding to other types in <code class="xref py py-mod docutils literal notranslate">collections.abc</code></a></li>
<li><a class="reference internal" href="#asynchronous-programming">Asynchronous programming</a></li>
<li><a class="reference internal" href="#context-manager-types">Context manager types</a></li>
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<li><a class="reference internal" href="#protocols">Protocols</a></li>
<li><a class="reference internal" href="#functions-and-decorators">Functions and decorators</a></li>
<li><a class="reference internal" href="#introspection-helpers">Introspection helpers</a></li>
<li><a class="reference internal" href="#constant">Constant</a></li>
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 <li class="nav-item nav-item-this"><a href=""><code class="xref py py-mod docutils literal notranslate">typing</code> — Support for type hints</a></li>
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 <section id="module-typing">
<h1><a class="reference internal" href="#module-typing" title="typing: Support for type hints (see :pep:`484`)."><code class="xref py py-mod docutils literal notranslate">typing</code></a> — Support for type hints<a class="headerlink" href="#module-typing" title="Permalink to this headline">¶</a></h1>
<div class="versionadded">
New in version 3.5.
</div>
Source code: <a class="reference external" href="https://github.com/python/cpython/tree/3.10/Lib/typing.py">Lib/typing.py</a>
<div class="admonition note">
Note
The Python runtime does not enforce function and variable type annotations.
They can be used by third party tools such as type checkers, IDEs, linters,
etc.
</div>
<hr class="docutils" />
This module provides runtime support for type hints. The most fundamental
support consists of the types <a class="reference internal" href="#typing.Any" title="typing.Any"><code class="xref py py-data docutils literal notranslate">Any</code></a>, <a class="reference internal" href="#typing.Union" title="typing.Union"><code class="xref py py-data docutils literal notranslate">Union</code></a>, <a class="reference internal" href="#typing.Callable" title="typing.Callable"><code class="xref py py-data docutils literal notranslate">Callable</code></a>,
<a class="reference internal" href="#typing.TypeVar" title="typing.TypeVar"><code class="xref py py-class docutils literal notranslate">TypeVar</code></a>, and <a class="reference internal" href="#typing.Generic" title="typing.Generic"><code class="xref py py-class docutils literal notranslate">Generic</code></a>. For a full specification, please see
<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0484">PEP 484</a>. For a simplified introduction to type hints, see <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0483">PEP 483</a>.
The function below takes and returns a string and is annotated as follows:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>def greeting(name: str) -&gt; str:
 return &#39;Hello &#39; + name
</pre></div>
</div>
In the function <code class="docutils literal notranslate">greeting</code>, the argument <code class="docutils literal notranslate">name</code> is expected to be of type
<a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> and the return type <a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a>. Subtypes are accepted as
arguments.
New features are frequently added to the <code class="docutils literal notranslate">typing</code> module.
The <a class="reference external" href="https://pypi.org/project/typing-extensions/">typing_extensions</a> package
provides backports of these new features to older versions of Python.
<div class="admonition seealso">
See also
For a quick overview of type hints, refer to
<a class="reference external" href="https://mypy.readthedocs.io/en/stable/cheat_sheet_py3.html">this cheat sheet</a>.
The “Type System Reference” section of <a class="reference external" href="https://mypy.readthedocs.io/">https://mypy.readthedocs.io/</a> – since
the Python typing system is standardised via PEPs, this reference should
broadly apply to most Python type checkers, although some parts may still be
specific to mypy.
The documentation at <a class="reference external" href="https://typing.readthedocs.io/">https://typing.readthedocs.io/</a> serves as useful reference
for type system features, useful typing related tools and typing best practices.
</div>
<section id="relevant-peps">
<h2>Relevant PEPs<a class="headerlink" href="#relevant-peps" title="Permalink to this headline">¶</a></h2>
Since the initial introduction of type hints in <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0484">PEP 484</a> and <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0483">PEP 483</a>, a
number of PEPs have modified and enhanced Python’s framework for type
annotations. These include:
<ul class="simple">
<li><dl class="simple">
<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0526">PEP 526</a>: Syntax for Variable Annotations</dt><dd>Introducing syntax for annotating variables outside of function
definitions, and <a class="reference internal" href="#typing.ClassVar" title="typing.ClassVar"><code class="xref py py-data docutils literal notranslate">ClassVar</code></a>
</dd>
</dl>
</li>
<li><dl class="simple">
<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0544">PEP 544</a>: Protocols: Structural subtyping (static duck typing)</dt><dd>Introducing <a class="reference internal" href="#typing.Protocol" title="typing.Protocol"><code class="xref py py-class docutils literal notranslate">Protocol</code></a> and the
<a class="reference internal" href="#typing.runtime_checkable" title="typing.runtime_checkable"><code class="xref py py-func docutils literal notranslate">&#64;runtime_checkable</code></a> decorator
</dd>
</dl>
</li>
<li><dl class="simple">
<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a>: Type Hinting Generics In Standard Collections</dt><dd>Introducing <a class="reference internal" href="types.html#types.GenericAlias" title="types.GenericAlias"><code class="xref py py-class docutils literal notranslate">types.GenericAlias</code></a> and the ability to use standard
library classes as <a class="reference internal" href="stdtypes.html#types-genericalias">generic types</a>
</dd>
</dl>
</li>
<li><dl class="simple">
<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0586">PEP 586</a>: Literal Types</dt><dd>Introducing <a class="reference internal" href="#typing.Literal" title="typing.Literal"><code class="xref py py-data docutils literal notranslate">Literal</code></a>
</dd>
</dl>
</li>
<li><dl class="simple">
<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0589">PEP 589</a>: TypedDict: Type Hints for Dictionaries with a Fixed Set of Keys</dt><dd>Introducing <a class="reference internal" href="#typing.TypedDict" title="typing.TypedDict"><code class="xref py py-class docutils literal notranslate">TypedDict</code></a>
</dd>
</dl>
</li>
<li><dl class="simple">
<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0591">PEP 591</a>: Adding a final qualifier to typing</dt><dd>Introducing <a class="reference internal" href="#typing.Final" title="typing.Final"><code class="xref py py-data docutils literal notranslate">Final</code></a> and the <a class="reference internal" href="#typing.final" title="typing.final"><code class="xref py py-func docutils literal notranslate">&#64;final</code></a> decorator
</dd>
</dl>
</li>
<li><dl class="simple">
<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0593">PEP 593</a>: Flexible function and variable annotations</dt><dd>Introducing <a class="reference internal" href="#typing.Annotated" title="typing.Annotated"><code class="xref py py-data docutils literal notranslate">Annotated</code></a>
</dd>
</dl>
</li>
<li><dl class="simple">
<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0604">PEP 604</a>: Allow writing union types as <code class="docutils literal notranslate">X | Y</code></dt><dd>Introducing <a class="reference internal" href="types.html#types.UnionType" title="types.UnionType"><code class="xref py py-data docutils literal notranslate">types.UnionType</code></a> and the ability to use
the binary-or operator <code class="docutils literal notranslate">|</code> to signify a
<a class="reference internal" href="stdtypes.html#types-union">union of types</a>
</dd>
</dl>
</li>
<li><dl class="simple">
<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0612">PEP 612</a>: Parameter Specification Variables</dt><dd>Introducing <a class="reference internal" href="#typing.ParamSpec" title="typing.ParamSpec"><code class="xref py py-class docutils literal notranslate">ParamSpec</code></a> and <a class="reference internal" href="#typing.Concatenate" title="typing.Concatenate"><code class="xref py py-data docutils literal notranslate">Concatenate</code></a>
</dd>
</dl>
</li>
<li><dl class="simple">
<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0613">PEP 613</a>: Explicit Type Aliases</dt><dd>Introducing <a class="reference internal" href="#typing.TypeAlias" title="typing.TypeAlias"><code class="xref py py-data docutils literal notranslate">TypeAlias</code></a>
</dd>
</dl>
</li>
<li><dl class="simple">
<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0647">PEP 647</a>: User-Defined Type Guards</dt><dd>Introducing <a class="reference internal" href="#typing.TypeGuard" title="typing.TypeGuard"><code class="xref py py-data docutils literal notranslate">TypeGuard</code></a>
</dd>
</dl>
</li>
</ul>
</section>
<section id="type-aliases">
<h2>Type aliases<a class="headerlink" href="#type-aliases" title="Permalink to this headline">¶</a></h2>
A type alias is defined by assigning the type to the alias. In this example,
<code class="docutils literal notranslate">Vector</code> and <code class="docutils literal notranslate">list[float]</code> will be treated as interchangeable synonyms:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>Vector = list[float]

def scale(scalar: float, vector: Vector) -&gt; Vector:
 return [scalar * num for num in vector]

# passes type checking; a list of floats qualifies as a Vector.
new_vector = scale(2.0, [1.0, -4.2, 5.4])
</pre></div>
</div>
Type aliases are useful for simplifying complex type signatures. For example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>from collections.abc import Sequence

ConnectionOptions = dict[str, str]
Address = tuple[str, int]
Server = tuple[Address, ConnectionOptions]

def broadcast_message(message: str, servers: Sequence[Server]) -&gt; None:
 ...

# The static type checker will treat the previous type signature as
# being exactly equivalent to this one.
def broadcast_message(
 message: str,
 servers: Sequence[tuple[tuple[str, int], dict[str, str]]]) -&gt; None:
 ...
</pre></div>
</div>
Note that <code class="docutils literal notranslate">None</code> as a type hint is a special case and is replaced by
<code class="docutils literal notranslate">type(None)</code>.
</section>
<section id="newtype">
<h2>NewType<a class="headerlink" href="#newtype" title="Permalink to this headline">¶</a></h2>
Use the <a class="reference internal" href="#typing.NewType" title="typing.NewType"><code class="xref py py-class docutils literal notranslate">NewType</code></a> helper to create distinct types:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>from typing import NewType

UserId = NewType(&#39;UserId&#39;, int)
some_id = UserId(524313)
</pre></div>
</div>
The static type checker will treat the new type as if it were a subclass
of the original type. This is useful in helping catch logical errors:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>def get_user_name(user_id: UserId) -&gt; str:
 ...

# passes type checking
user_a = get_user_name(UserId(42351))

# fails type checking; an int is not a UserId
user_b = get_user_name(-1)
</pre></div>
</div>
You may still perform all <code class="docutils literal notranslate">int</code> operations on a variable of type <code class="docutils literal notranslate">UserId</code>,
but the result will always be of type <code class="docutils literal notranslate">int</code>. This lets you pass in a
<code class="docutils literal notranslate">UserId</code> wherever an <code class="docutils literal notranslate">int</code> might be expected, but will prevent you from
accidentally creating a <code class="docutils literal notranslate">UserId</code> in an invalid way:
<div class="highlight-python3 notranslate"><div class="highlight"><pre># &#39;output&#39; is of type &#39;int&#39;, not &#39;UserId&#39;
output = UserId(23413) + UserId(54341)
</pre></div>
</div>
Note that these checks are enforced only by the static type checker. At runtime,
the statement <code class="docutils literal notranslate">Derived = NewType('Derived', Base)</code> will make <code class="docutils literal notranslate">Derived</code> a
callable that immediately returns whatever parameter you pass it. That means
the expression <code class="docutils literal notranslate">Derived(some_value)</code> does not create a new class or introduce
much overhead beyond that of a regular function call.
More precisely, the expression <code class="docutils literal notranslate">some_value is Derived(some_value)</code> is always
true at runtime.
It is invalid to create a subtype of <code class="docutils literal notranslate">Derived</code>:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>from typing import NewType

# Fails at runtime and does not pass type checking
class AdminUserId(UserId): pass
</pre></div>
</div>
However, it is possible to create a <a class="reference internal" href="#typing.NewType" title="typing.NewType"><code class="xref py py-class docutils literal notranslate">NewType</code></a> based on a ‘derived’ <code class="docutils literal notranslate">NewType</code>:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>from typing import NewType

ProUserId = NewType(&#39;ProUserId&#39;, UserId)
</pre></div>
</div>
and typechecking for <code class="docutils literal notranslate">ProUserId</code> will work as expected.
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0484">PEP 484</a> for more details.
<div class="admonition note">
Note
Recall that the use of a type alias declares two types to be equivalent to
one another. Doing <code class="docutils literal notranslate">Alias = Original</code> will make the static type checker
treat <code class="docutils literal notranslate">Alias</code> as being exactly equivalent to <code class="docutils literal notranslate">Original</code> in all cases.
This is useful when you want to simplify complex type signatures.
In contrast, <code class="docutils literal notranslate">NewType</code> declares one type to be a subtype of another.
Doing <code class="docutils literal notranslate">Derived = NewType('Derived', Original)</code> will make the static type
checker treat <code class="docutils literal notranslate">Derived</code> as a subclass of <code class="docutils literal notranslate">Original</code>, which means a
value of type <code class="docutils literal notranslate">Original</code> cannot be used in places where a value of type
<code class="docutils literal notranslate">Derived</code> is expected. This is useful when you want to prevent logic
errors with minimal runtime cost.
</div>
<div class="versionadded">
New in version 3.5.2.
</div>
<div class="versionchanged">
Changed in version 3.10: <code class="docutils literal notranslate">NewType</code> is now a class rather than a function. There is some additional
runtime cost when calling <code class="docutils literal notranslate">NewType</code> over a regular function. However, this
cost will be reduced in 3.11.0.
</div>
</section>
<section id="callable">
<h2>Callable<a class="headerlink" href="#callable" title="Permalink to this headline">¶</a></h2>
Frameworks expecting callback functions of specific signatures might be
type hinted using <code class="docutils literal notranslate">Callable[[Arg1Type, Arg2Type], ReturnType]</code>.
For example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>from collections.abc import Callable

def feeder(get_next_item: Callable[[], str]) -&gt; None:
 # Body

def async_query(on_success: Callable[[int], None],
 on_error: Callable[[int, Exception], None]) -&gt; None:
 # Body

async def on_update(value: str) -&gt; None:
 # Body
callback: Callable[[str], Awaitable[None]] = on_update
</pre></div>
</div>
It is possible to declare the return type of a callable without specifying
the call signature by substituting a literal ellipsis
for the list of arguments in the type hint: <code class="docutils literal notranslate">Callable[..., ReturnType]</code>.
Callables which take other callables as arguments may indicate that their
parameter types are dependent on each other using <a class="reference internal" href="#typing.ParamSpec" title="typing.ParamSpec"><code class="xref py py-class docutils literal notranslate">ParamSpec</code></a>.
Additionally, if that callable adds or removes arguments from other
callables, the <a class="reference internal" href="#typing.Concatenate" title="typing.Concatenate"><code class="xref py py-data docutils literal notranslate">Concatenate</code></a> operator may be used. They
take the form <code class="docutils literal notranslate">Callable[ParamSpecVariable, ReturnType]</code> and
<code class="docutils literal notranslate">Callable[Concatenate[Arg1Type, Arg2Type, ..., ParamSpecVariable], ReturnType]</code>
respectively.
<div class="versionchanged">
Changed in version 3.10: <code class="docutils literal notranslate">Callable</code> now supports <a class="reference internal" href="#typing.ParamSpec" title="typing.ParamSpec"><code class="xref py py-class docutils literal notranslate">ParamSpec</code></a> and <a class="reference internal" href="#typing.Concatenate" title="typing.Concatenate"><code class="xref py py-data docutils literal notranslate">Concatenate</code></a>.
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0612">PEP 612</a> for more details.
</div>
<div class="admonition seealso">
See also
The documentation for <a class="reference internal" href="#typing.ParamSpec" title="typing.ParamSpec"><code class="xref py py-class docutils literal notranslate">ParamSpec</code></a> and <a class="reference internal" href="#typing.Concatenate" title="typing.Concatenate"><code class="xref py py-class docutils literal notranslate">Concatenate</code></a> provides
examples of usage in <code class="docutils literal notranslate">Callable</code>.
</div>
</section>
<section id="generics">
<h2>Generics<a class="headerlink" href="#generics" title="Permalink to this headline">¶</a></h2>
Since type information about objects kept in containers cannot be statically
inferred in a generic way, abstract base classes have been extended to support
subscription to denote expected types for container elements.
<div class="highlight-python3 notranslate"><div class="highlight"><pre>from collections.abc import Mapping, Sequence

def notify_by_email(employees: Sequence[Employee],
 overrides: Mapping[str, str]) -&gt; None: ...
</pre></div>
</div>
Generics can be parameterized by using a factory available in typing
called <a class="reference internal" href="#typing.TypeVar" title="typing.TypeVar"><code class="xref py py-class docutils literal notranslate">TypeVar</code></a>.
<div class="highlight-python3 notranslate"><div class="highlight"><pre>from collections.abc import Sequence
from typing import TypeVar

def first(l: Sequence[T]) -&gt; T: # Generic function
 return l[0]
</pre></div>
</div>
</section>
<section id="user-defined-generic-types">
<h2>User-defined generic types<a class="headerlink" href="#user-defined-generic-types" title="Permalink to this headline">¶</a></h2>
A user-defined class can be defined as a generic class.
<div class="highlight-python3 notranslate"><div class="highlight"><pre>from typing import TypeVar, Generic
from logging import Logger

T = TypeVar(&#39;T&#39;)

class LoggedVar(Generic[T]):
 def __init__(self, value: T, name: str, logger: Logger) -&gt; None:
 self.name = name
 self.logger = logger
 self.value = value

def set(self, new: T) -&gt; None:
 self.log(&#39;Set &#39; + repr(self.value))
 self.value = new

def get(self) -&gt; T:
 self.log(&#39;Get &#39; + repr(self.value))
 return self.value

def log(self, message: str) -&gt; None:
 self.logger.info(&#39;%s: %s&#39;, self.name, message)
</pre></div>
</div>
<code class="docutils literal notranslate">Generic[T]</code> as a base class defines that the class <code class="docutils literal notranslate">LoggedVar</code> takes a
single type parameter <code class="docutils literal notranslate">T</code> . This also makes <code class="docutils literal notranslate">T</code> valid as a type within the
class body.
The <a class="reference internal" href="#typing.Generic" title="typing.Generic"><code class="xref py py-class docutils literal notranslate">Generic</code></a> base class defines <a class="reference internal" href="../reference/datamodel.html#object.__class_getitem__" title="object.__class_getitem__"><code class="xref py py-meth docutils literal notranslate">__class_getitem__()</code></a> so
that <code class="docutils literal notranslate">LoggedVar[T]</code> is valid as a type:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>from collections.abc import Iterable

def zero_all_vars(vars: Iterable[LoggedVar[int]]) -&gt; None:
 for var in vars:
 var.set(0)
</pre></div>
</div>
A generic type can have any number of type variables. All varieties of
<a class="reference internal" href="#typing.TypeVar" title="typing.TypeVar"><code class="xref py py-class docutils literal notranslate">TypeVar</code></a> are permissible as parameters for a generic type:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>from typing import TypeVar, Generic, Sequence

T = TypeVar(&#39;T&#39;, contravariant=True)
B = TypeVar(&#39;B&#39;, bound=Sequence[bytes], covariant=True)
S = TypeVar(&#39;S&#39;, int, str)

class WeirdTrio(Generic[T, B, S]):
 ...
</pre></div>
</div>
Each type variable argument to <a class="reference internal" href="#typing.Generic" title="typing.Generic"><code class="xref py py-class docutils literal notranslate">Generic</code></a> must be distinct.
This is thus invalid:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>from typing import TypeVar, Generic
...

T = TypeVar(&#39;T&#39;)

class Pair(Generic[T, T]): # INVALID
 ...
</pre></div>
</div>
You can use multiple inheritance with <a class="reference internal" href="#typing.Generic" title="typing.Generic"><code class="xref py py-class docutils literal notranslate">Generic</code></a>:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>from collections.abc import Sized
from typing import TypeVar, Generic

T = TypeVar(&#39;T&#39;)

class LinkedList(Sized, Generic[T]):
 ...
</pre></div>
</div>
When inheriting from generic classes, some type variables could be fixed:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>from collections.abc import Mapping
from typing import TypeVar

T = TypeVar(&#39;T&#39;)

class MyDict(Mapping[str, T]):
 ...
</pre></div>
</div>
In this case <code class="docutils literal notranslate">MyDict</code> has a single parameter, <code class="docutils literal notranslate">T</code>.
Using a generic class without specifying type parameters assumes
<a class="reference internal" href="#typing.Any" title="typing.Any"><code class="xref py py-data docutils literal notranslate">Any</code></a> for each position. In the following example, <code class="docutils literal notranslate">MyIterable</code> is
not generic but implicitly inherits from <code class="docutils literal notranslate">Iterable[Any]</code>:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>from collections.abc import Iterable

class MyIterable(Iterable): # Same as Iterable[Any]
</pre></div>
</div>
User defined generic type aliases are also supported. Examples:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>from collections.abc import Iterable
from typing import TypeVar
S = TypeVar(&#39;S&#39;)
Response = Iterable[S] | int

# Return type here is same as Iterable[str] | int
def response(query: str) -&gt; Response[str]:
 ...

def inproduct(v: Vec[T]) -&gt; T: # Same as Iterable[tuple[T, T]]
 return sum(x*y for x, y in v)
</pre></div>
</div>
<div class="versionchanged">
Changed in version 3.7: <a class="reference internal" href="#typing.Generic" title="typing.Generic"><code class="xref py py-class docutils literal notranslate">Generic</code></a> no longer has a custom metaclass.
</div>
User-defined generics for parameter expressions are also supported via parameter
specification variables in the form <code class="docutils literal notranslate">Generic[P]</code>. The behavior is consistent
with type variables’ described above as parameter specification variables are
treated by the typing module as a specialized type variable. The one exception
to this is that a list of types can be used to substitute a <a class="reference internal" href="#typing.ParamSpec" title="typing.ParamSpec"><code class="xref py py-class docutils literal notranslate">ParamSpec</code></a>:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; from typing import Generic, ParamSpec, TypeVar

&gt;&gt;&gt; T = TypeVar(&#39;T&#39;)
&gt;&gt;&gt; P = ParamSpec(&#39;P&#39;)

&gt;&gt;&gt; class Z(Generic[T, P]): ...
...
&gt;&gt;&gt; Z[int, [dict, float]]
__main__.Z[int, (&lt;class &#39;dict&#39;&gt;, &lt;class &#39;float&#39;&gt;)]
</pre></div>
</div>
Furthermore, a generic with only one parameter specification variable will accept
parameter lists in the forms <code class="docutils literal notranslate">X[[Type1, Type2, ...]]</code> and also
<code class="docutils literal notranslate">X[Type1, Type2, ...]</code> for aesthetic reasons. Internally, the latter is converted
to the former, so the following are equivalent:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; class X(Generic[P]): ...
...
&gt;&gt;&gt; X[int, str]
__main__.X[(&lt;class &#39;int&#39;&gt;, &lt;class &#39;str&#39;&gt;)]
&gt;&gt;&gt; X[[int, str]]
__main__.X[(&lt;class &#39;int&#39;&gt;, &lt;class &#39;str&#39;&gt;)]
</pre></div>
</div>
Do note that generics with <a class="reference internal" href="#typing.ParamSpec" title="typing.ParamSpec"><code class="xref py py-class docutils literal notranslate">ParamSpec</code></a> may not have correct
<code class="docutils literal notranslate">__parameters__</code> after substitution in some cases because they
are intended primarily for static type checking.
<div class="versionchanged">
Changed in version 3.10: <a class="reference internal" href="#typing.Generic" title="typing.Generic"><code class="xref py py-class docutils literal notranslate">Generic</code></a> can now be parameterized over parameter expressions.
See <a class="reference internal" href="#typing.ParamSpec" title="typing.ParamSpec"><code class="xref py py-class docutils literal notranslate">ParamSpec</code></a> and <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0612">PEP 612</a> for more details.
</div>
A user-defined generic class can have ABCs as base classes without a metaclass
conflict. Generic metaclasses are not supported. The outcome of parameterizing
generics is cached, and most types in the typing module are <a class="reference internal" href="../glossary.html#term-hashable">hashable</a> and
comparable for equality.
</section>
<section id="the-any-type">
<h2>The <a class="reference internal" href="#typing.Any" title="typing.Any"><code class="xref py py-data docutils literal notranslate">Any</code></a> type<a class="headerlink" href="#the-any-type" title="Permalink to this headline">¶</a></h2>
A special kind of type is <a class="reference internal" href="#typing.Any" title="typing.Any"><code class="xref py py-data docutils literal notranslate">Any</code></a>. A static type checker will treat
every type as being compatible with <a class="reference internal" href="#typing.Any" title="typing.Any"><code class="xref py py-data docutils literal notranslate">Any</code></a> and <a class="reference internal" href="#typing.Any" title="typing.Any"><code class="xref py py-data docutils literal notranslate">Any</code></a> as being
compatible with every type.
This means that it is possible to perform any operation or method call on a
value of type <a class="reference internal" href="#typing.Any" title="typing.Any"><code class="xref py py-data docutils literal notranslate">Any</code></a> and assign it to any variable:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>from typing import Any

a: Any = None
a = [] # OK
a = 2 # OK

s: str = &#39;&#39;
s = a # OK

def foo(item: Any) -&gt; int:
 # Passes type checking; &#39;item&#39; could be any type,
 # and that type might have a &#39;bar&#39; method
 item.bar()
 ...
</pre></div>
</div>
Notice that no type checking is performed when assigning a value of type
<a class="reference internal" href="#typing.Any" title="typing.Any"><code class="xref py py-data docutils literal notranslate">Any</code></a> to a more precise type. For example, the static type checker did
not report an error when assigning <code class="docutils literal notranslate">a</code> to <code class="docutils literal notranslate">s</code> even though <code class="docutils literal notranslate">s</code> was
declared to be of type <a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> and receives an <a class="reference internal" href="functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a> value at
runtime!
Furthermore, all functions without a return type or parameter types will
implicitly default to using <a class="reference internal" href="#typing.Any" title="typing.Any"><code class="xref py py-data docutils literal notranslate">Any</code></a>:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>def legacy_parser(text):
 ...
 return data

# A static type checker will treat the above
# as having the same signature as:
def legacy_parser(text: Any) -&gt; Any:
 ...
 return data
</pre></div>
</div>
This behavior allows <a class="reference internal" href="#typing.Any" title="typing.Any"><code class="xref py py-data docutils literal notranslate">Any</code></a> to be used as an escape hatch when you
need to mix dynamically and statically typed code.
Contrast the behavior of <a class="reference internal" href="#typing.Any" title="typing.Any"><code class="xref py py-data docutils literal notranslate">Any</code></a> with the behavior of <a class="reference internal" href="functions.html#object" title="object"><code class="xref py py-class docutils literal notranslate">object</code></a>.
Similar to <a class="reference internal" href="#typing.Any" title="typing.Any"><code class="xref py py-data docutils literal notranslate">Any</code></a>, every type is a subtype of <a class="reference internal" href="functions.html#object" title="object"><code class="xref py py-class docutils literal notranslate">object</code></a>. However,
unlike <a class="reference internal" href="#typing.Any" title="typing.Any"><code class="xref py py-data docutils literal notranslate">Any</code></a>, the reverse is not true: <a class="reference internal" href="functions.html#object" title="object"><code class="xref py py-class docutils literal notranslate">object</code></a> is not a
subtype of every other type.
That means when the type of a value is <a class="reference internal" href="functions.html#object" title="object"><code class="xref py py-class docutils literal notranslate">object</code></a>, a type checker will
reject almost all operations on it, and assigning it to a variable (or using
it as a return value) of a more specialized type is a type error. For example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>def hash_a(item: object) -&gt; int:
 # Fails type checking; an object does not have a &#39;magic&#39; method.
 item.magic()
 ...

def hash_b(item: Any) -&gt; int:
 # Passes type checking
 item.magic()
 ...

# Passes type checking, since ints and strs are subclasses of object
hash_a(42)
hash_a(&quot;foo&quot;)

# Passes type checking, since Any is compatible with all types
hash_b(42)
hash_b(&quot;foo&quot;)
</pre></div>
</div>
Use <a class="reference internal" href="functions.html#object" title="object"><code class="xref py py-class docutils literal notranslate">object</code></a> to indicate that a value could be any type in a typesafe
manner. Use <a class="reference internal" href="#typing.Any" title="typing.Any"><code class="xref py py-data docutils literal notranslate">Any</code></a> to indicate that a value is dynamically typed.
</section>
<section id="nominal-vs-structural-subtyping">
<h2>Nominal vs structural subtyping<a class="headerlink" href="#nominal-vs-structural-subtyping" title="Permalink to this headline">¶</a></h2>
Initially <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0484">PEP 484</a> defined the Python static type system as using
nominal subtyping. This means that a class <code class="docutils literal notranslate">A</code> is allowed where
a class <code class="docutils literal notranslate">B</code> is expected if and only if <code class="docutils literal notranslate">A</code> is a subclass of <code class="docutils literal notranslate">B</code>.
This requirement previously also applied to abstract base classes, such as
<a class="reference internal" href="collections.abc.html#collections.abc.Iterable" title="collections.abc.Iterable"><code class="xref py py-class docutils literal notranslate">Iterable</code></a>. The problem with this approach is that a class had
to be explicitly marked to support them, which is unpythonic and unlike
what one would normally do in idiomatic dynamically typed Python code.
For example, this conforms to <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0484">PEP 484</a>:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>from collections.abc import Sized, Iterable, Iterator

class Bucket(Sized, Iterable[int]):
 ...
 def __len__(self) -&gt; int: ...
 def __iter__(self) -&gt; Iterator[int]: ...
</pre></div>
</div>
<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0544">PEP 544</a> allows to solve this problem by allowing users to write
the above code without explicit base classes in the class definition,
allowing <code class="docutils literal notranslate">Bucket</code> to be implicitly considered a subtype of both <code class="docutils literal notranslate">Sized</code>
and <code class="docutils literal notranslate">Iterable[int]</code> by static type checkers. This is known as
structural subtyping (or static duck-typing):
<div class="highlight-python3 notranslate"><div class="highlight"><pre>from collections.abc import Iterator, Iterable

class Bucket: # Note: no base classes
 ...
 def __len__(self) -&gt; int: ...
 def __iter__(self) -&gt; Iterator[int]: ...

def collect(items: Iterable[int]) -&gt; int: ...
result = collect(Bucket()) # Passes type check
</pre></div>
</div>
Moreover, by subclassing a special class <a class="reference internal" href="#typing.Protocol" title="typing.Protocol"><code class="xref py py-class docutils literal notranslate">Protocol</code></a>, a user
can define new custom protocols to fully enjoy structural subtyping
(see examples below).
</section>
<section id="module-contents">
<h2>Module contents<a class="headerlink" href="#module-contents" title="Permalink to this headline">¶</a></h2>
The module defines the following classes, functions and decorators.
<div class="admonition note">
Note
This module defines several types that are subclasses of pre-existing
standard library classes which also extend <a class="reference internal" href="#typing.Generic" title="typing.Generic"><code class="xref py py-class docutils literal notranslate">Generic</code></a>
to support type variables inside <code class="docutils literal notranslate">[]</code>.
These types became redundant in Python 3.9 when the
corresponding pre-existing classes were enhanced to support <code class="docutils literal notranslate">[]</code>.
The redundant types are deprecated as of Python 3.9 but no
deprecation warnings will be issued by the interpreter.
It is expected that type checkers will flag the deprecated types
when the checked program targets Python 3.9 or newer.
The deprecated types will be removed from the <a class="reference internal" href="#module-typing" title="typing: Support for type hints (see :pep:`484`)."><code class="xref py py-mod docutils literal notranslate">typing</code></a> module
in the first Python version released 5 years after the release of Python 3.9.0.
See details in <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a>—Type Hinting Generics In Standard Collections.
</div>
<section id="special-typing-primitives">
<h3>Special typing primitives<a class="headerlink" href="#special-typing-primitives" title="Permalink to this headline">¶</a></h3>
<section id="special-types">
<h4>Special types<a class="headerlink" href="#special-types" title="Permalink to this headline">¶</a></h4>
These can be used as types in annotations and do not support <code class="docutils literal notranslate">[]</code>.
<dl class="py data">
<dt class="sig sig-object py" id="typing.Any">
typing.Any<a class="headerlink" href="#typing.Any" title="Permalink to this definition">¶</a></dt>
<dd>Special type indicating an unconstrained type.
<ul class="simple">
<li>Every type is compatible with <a class="reference internal" href="#typing.Any" title="typing.Any"><code class="xref py py-data docutils literal notranslate">Any</code></a>.</li>
<li><a class="reference internal" href="#typing.Any" title="typing.Any"><code class="xref py py-data docutils literal notranslate">Any</code></a> is compatible with every type.</li>
</ul>
</dd></dl>

<dl class="py data">
<dt class="sig sig-object py" id="typing.NoReturn">
typing.NoReturn<a class="headerlink" href="#typing.NoReturn" title="Permalink to this definition">¶</a></dt>
<dd>Special type indicating that a function never returns.
For example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>from typing import NoReturn

def stop() -&gt; NoReturn:
 raise RuntimeError(&#39;no way&#39;)
</pre></div>
</div>
<div class="versionadded">
New in version 3.5.4.
</div>
<div class="versionadded">
New in version 3.6.2.
</div>
</dd></dl>

<dl class="py data">
<dt class="sig sig-object py" id="typing.TypeAlias">
typing.TypeAlias<a class="headerlink" href="#typing.TypeAlias" title="Permalink to this definition">¶</a></dt>
<dd>Special annotation for explicitly declaring a <a class="reference internal" href="#type-aliases">type alias</a>.
For example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>from typing import TypeAlias

Factors: TypeAlias = list[int]
</pre></div>
</div>
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0613">PEP 613</a> for more details about explicit type aliases.
<div class="versionadded">
New in version 3.10.
</div>
</dd></dl>

</section>
<section id="special-forms">
<h4>Special forms<a class="headerlink" href="#special-forms" title="Permalink to this headline">¶</a></h4>
These can be used as types in annotations using <code class="docutils literal notranslate">[]</code>, each having a unique syntax.
<dl class="py data">
<dt class="sig sig-object py" id="typing.Tuple">
typing.Tuple<a class="headerlink" href="#typing.Tuple" title="Permalink to this definition">¶</a></dt>
<dd>Tuple type; <code class="docutils literal notranslate">Tuple[X, Y]</code> is the type of a tuple of two items
with the first item of type X and the second of type Y. The type of
the empty tuple can be written as <code class="docutils literal notranslate">Tuple[()]</code>.
Example: <code class="docutils literal notranslate">Tuple[T1, T2]</code> is a tuple of two elements corresponding
to type variables T1 and T2. <code class="docutils literal notranslate">Tuple[int, float, str]</code> is a tuple
of an int, a float and a string.
To specify a variable-length tuple of homogeneous type,
use literal ellipsis, e.g. <code class="docutils literal notranslate">Tuple[int, ...]</code>. A plain <a class="reference internal" href="#typing.Tuple" title="typing.Tuple"><code class="xref py py-data docutils literal notranslate">Tuple</code></a>
is equivalent to <code class="docutils literal notranslate">Tuple[Any, ...]</code>, and in turn to <a class="reference internal" href="stdtypes.html#tuple" title="tuple"><code class="xref py py-class docutils literal notranslate">tuple</code></a>.
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="stdtypes.html#tuple" title="tuple"><code class="xref py py-class docutils literal notranslate">builtins.tuple</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py data">
<dt class="sig sig-object py" id="typing.Union">
typing.Union<a class="headerlink" href="#typing.Union" title="Permalink to this definition">¶</a></dt>
<dd>Union type; <code class="docutils literal notranslate">Union[X, Y]</code> is equivalent to <code class="docutils literal notranslate">X | Y</code> and means either X or Y.
To define a union, use e.g. <code class="docutils literal notranslate">Union[int, str]</code> or the shorthand <code class="docutils literal notranslate">int | str</code>. Using that shorthand is recommended. Details:
<ul>
<li>The arguments must be types and there must be at least one.</li>
<li>Unions of unions are flattened, e.g.:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>Union[Union[int, str], float] == Union[int, str, float]
</pre></div>
</div>
</li>
<li>Unions of a single argument vanish, e.g.:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>Union[int] == int # The constructor actually returns int
</pre></div>
</div>
</li>
<li>Redundant arguments are skipped, e.g.:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>Union[int, str, int] == Union[int, str] == int | str
</pre></div>
</div>
</li>
<li>When comparing unions, the argument order is ignored, e.g.:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>Union[int, str] == Union[str, int]
</pre></div>
</div>
</li>
<li>You cannot subclass or instantiate a <code class="docutils literal notranslate">Union</code>.</li>
<li>You cannot write <code class="docutils literal notranslate">Union[X][Y]</code>.</li>
</ul>
<div class="versionchanged">
Changed in version 3.7: Don’t remove explicit subclasses from unions at runtime.
</div>
<div class="versionchanged">
Changed in version 3.10: Unions can now be written as <code class="docutils literal notranslate">X | Y</code>. See
<a class="reference internal" href="stdtypes.html#types-union">union type expressions</a>.
</div>
</dd></dl>

<dl class="py data">
<dt class="sig sig-object py" id="typing.Optional">
typing.Optional<a class="headerlink" href="#typing.Optional" title="Permalink to this definition">¶</a></dt>
<dd>Optional type.
<code class="docutils literal notranslate">Optional[X]</code> is equivalent to <code class="docutils literal notranslate">X | None</code> (or <code class="docutils literal notranslate">Union[X, None]</code>).
Note that this is not the same concept as an optional argument,
which is one that has a default. An optional argument with a
default does not require the <code class="docutils literal notranslate">Optional</code> qualifier on its type
annotation just because it is optional. For example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>def foo(arg: int = 0) -&gt; None:
 ...
</pre></div>
</div>
On the other hand, if an explicit value of <code class="docutils literal notranslate">None</code> is allowed, the
use of <code class="docutils literal notranslate">Optional</code> is appropriate, whether the argument is optional
or not. For example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>def foo(arg: Optional[int] = None) -&gt; None:
 ...
</pre></div>
</div>
<div class="versionchanged">
Changed in version 3.10: Optional can now be written as <code class="docutils literal notranslate">X | None</code>. See
<a class="reference internal" href="stdtypes.html#types-union">union type expressions</a>.
</div>
</dd></dl>

<dl class="py data">
<dt class="sig sig-object py" id="typing.Callable">
typing.Callable<a class="headerlink" href="#typing.Callable" title="Permalink to this definition">¶</a></dt>
<dd>Callable type; <code class="docutils literal notranslate">Callable[[int], str]</code> is a function of (int) -&gt; str.
The subscription syntax must always be used with exactly two
values: the argument list and the return type. The argument list
must be a list of types or an ellipsis; the return type must be
a single type.
There is no syntax to indicate optional or keyword arguments;
such function types are rarely used as callback types.
<code class="docutils literal notranslate">Callable[..., ReturnType]</code> (literal ellipsis) can be used to
type hint a callable taking any number of arguments and returning
<code class="docutils literal notranslate">ReturnType</code>. A plain <a class="reference internal" href="#typing.Callable" title="typing.Callable"><code class="xref py py-data docutils literal notranslate">Callable</code></a> is equivalent to
<code class="docutils literal notranslate">Callable[..., Any]</code>, and in turn to
<a class="reference internal" href="collections.abc.html#collections.abc.Callable" title="collections.abc.Callable"><code class="xref py py-class docutils literal notranslate">collections.abc.Callable</code></a>.
Callables which take other callables as arguments may indicate that their
parameter types are dependent on each other using <a class="reference internal" href="#typing.ParamSpec" title="typing.ParamSpec"><code class="xref py py-class docutils literal notranslate">ParamSpec</code></a>.
Additionally, if that callable adds or removes arguments from other
callables, the <a class="reference internal" href="#typing.Concatenate" title="typing.Concatenate"><code class="xref py py-data docutils literal notranslate">Concatenate</code></a> operator may be used. They
take the form <code class="docutils literal notranslate">Callable[ParamSpecVariable, ReturnType]</code> and
<code class="docutils literal notranslate">Callable[Concatenate[Arg1Type, Arg2Type, ..., ParamSpecVariable], ReturnType]</code>
respectively.
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="collections.abc.html#collections.abc.Callable" title="collections.abc.Callable"><code class="xref py py-class docutils literal notranslate">collections.abc.Callable</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
<div class="versionchanged">
Changed in version 3.10: <code class="docutils literal notranslate">Callable</code> now supports <a class="reference internal" href="#typing.ParamSpec" title="typing.ParamSpec"><code class="xref py py-class docutils literal notranslate">ParamSpec</code></a> and <a class="reference internal" href="#typing.Concatenate" title="typing.Concatenate"><code class="xref py py-data docutils literal notranslate">Concatenate</code></a>.
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0612">PEP 612</a> for more details.
</div>
<div class="admonition seealso">
See also
The documentation for <a class="reference internal" href="#typing.ParamSpec" title="typing.ParamSpec"><code class="xref py py-class docutils literal notranslate">ParamSpec</code></a> and <a class="reference internal" href="#typing.Concatenate" title="typing.Concatenate"><code class="xref py py-class docutils literal notranslate">Concatenate</code></a> provide
examples of usage with <code class="docutils literal notranslate">Callable</code>.
</div>
</dd></dl>

<dl class="py data">
<dt class="sig sig-object py" id="typing.Concatenate">
typing.Concatenate<a class="headerlink" href="#typing.Concatenate" title="Permalink to this definition">¶</a></dt>
<dd>Used with <a class="reference internal" href="#typing.Callable" title="typing.Callable"><code class="xref py py-data docutils literal notranslate">Callable</code></a> and <a class="reference internal" href="#typing.ParamSpec" title="typing.ParamSpec"><code class="xref py py-class docutils literal notranslate">ParamSpec</code></a> to type annotate a higher
order callable which adds, removes, or transforms parameters of another
callable. Usage is in the form
<code class="docutils literal notranslate">Concatenate[Arg1Type, Arg2Type, ..., ParamSpecVariable]</code>. <code class="docutils literal notranslate">Concatenate</code>
is currently only valid when used as the first argument to a <a class="reference internal" href="#typing.Callable" title="typing.Callable"><code class="xref py py-data docutils literal notranslate">Callable</code></a>.
The last parameter to <code class="docutils literal notranslate">Concatenate</code> must be a <a class="reference internal" href="#typing.ParamSpec" title="typing.ParamSpec"><code class="xref py py-class docutils literal notranslate">ParamSpec</code></a>.
For example, to annotate a decorator <code class="docutils literal notranslate">with_lock</code> which provides a
<a class="reference internal" href="threading.html#threading.Lock" title="threading.Lock"><code class="xref py py-class docutils literal notranslate">threading.Lock</code></a> to the decorated function, <code class="docutils literal notranslate">Concatenate</code> can be
used to indicate that <code class="docutils literal notranslate">with_lock</code> expects a callable which takes in a
<code class="docutils literal notranslate">Lock</code> as the first argument, and returns a callable with a different type
signature. In this case, the <a class="reference internal" href="#typing.ParamSpec" title="typing.ParamSpec"><code class="xref py py-class docutils literal notranslate">ParamSpec</code></a> indicates that the returned
callable’s parameter types are dependent on the parameter types of the
callable being passed in:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>from collections.abc import Callable
from threading import Lock
from typing import Concatenate, ParamSpec, TypeVar

P = ParamSpec(&#39;P&#39;)
R = TypeVar(&#39;R&#39;)

# Use this lock to ensure that only one thread is executing a function
# at any time.
my_lock = Lock()

def with_lock(f: Callable[Concatenate[Lock, P], R]) -&gt; Callable[P, R]:
 &#39;&#39;&#39;A type-safe decorator which provides a lock.&#39;&#39;&#39;
 def inner(*args: P.args, **kwargs: P.kwargs) -&gt; R:
 # Provide the lock as the first argument.
 return f(my_lock, *args, **kwargs)
 return inner

@with_lock
def sum_threadsafe(lock: Lock, numbers: list[float]) -&gt; float:
 &#39;&#39;&#39;Add a list of numbers together in a thread-safe manner.&#39;&#39;&#39;
 with lock:
 return sum(numbers)

# We don&#39;t need to pass in the lock ourselves thanks to the decorator.
sum_threadsafe([1.1, 2.2, 3.3])
</pre></div>
</div>
</dd></dl>

<div class="versionadded">
New in version 3.10.
</div>
<div class="admonition seealso">
See also
<ul class="simple">
<li><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0612">PEP 612</a> – Parameter Specification Variables (the PEP which introduced
<code class="docutils literal notranslate">ParamSpec</code> and <code class="docutils literal notranslate">Concatenate</code>).</li>
<li><a class="reference internal" href="#typing.ParamSpec" title="typing.ParamSpec"><code class="xref py py-class docutils literal notranslate">ParamSpec</code></a> and <a class="reference internal" href="#typing.Callable" title="typing.Callable"><code class="xref py py-class docutils literal notranslate">Callable</code></a>.</li>
</ul>
</div>
<dl class="py class">
<dt class="sig sig-object py" id="typing.Type">
class typing.Type(Generic[CT_co])<a class="headerlink" href="#typing.Type" title="Permalink to this definition">¶</a></dt>
<dd>A variable annotated with <code class="docutils literal notranslate">C</code> may accept a value of type <code class="docutils literal notranslate">C</code>. In
contrast, a variable annotated with <code class="docutils literal notranslate">Type[C]</code> may accept values that are
classes themselves – specifically, it will accept the class object of
<code class="docutils literal notranslate">C</code>. For example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>a = 3 # Has type &#39;int&#39;
b = int # Has type &#39;Type[int]&#39;
c = type(a) # Also has type &#39;Type[int]&#39;
</pre></div>
</div>
Note that <code class="docutils literal notranslate">Type[C]</code> is covariant:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>class User: ...
class BasicUser(User): ...
class ProUser(User): ...
class TeamUser(User): ...

# Accepts User, BasicUser, ProUser, TeamUser, ...
def make_new_user(user_class: Type[User]) -&gt; User:
 # ...
 return user_class()
</pre></div>
</div>
The fact that <code class="docutils literal notranslate">Type[C]</code> is covariant implies that all subclasses of
<code class="docutils literal notranslate">C</code> should implement the same constructor signature and class method
signatures as <code class="docutils literal notranslate">C</code>. The type checker should flag violations of this,
but should also allow constructor calls in subclasses that match the
constructor calls in the indicated base class. How the type checker is
required to handle this particular case may change in future revisions of
<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0484">PEP 484</a>.
The only legal parameters for <a class="reference internal" href="#typing.Type" title="typing.Type"><code class="xref py py-class docutils literal notranslate">Type</code></a> are classes, <a class="reference internal" href="#typing.Any" title="typing.Any"><code class="xref py py-data docutils literal notranslate">Any</code></a>,
<a class="reference internal" href="#generics">type variables</a>, and unions of any of these types.
For example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>def new_non_team_user(user_class: Type[BasicUser | ProUser]): ...
</pre></div>
</div>
<code class="docutils literal notranslate">Type[Any]</code> is equivalent to <code class="docutils literal notranslate">Type</code> which in turn is equivalent
to <code class="docutils literal notranslate">type</code>, which is the root of Python’s metaclass hierarchy.
<div class="versionadded">
New in version 3.5.2.
</div>
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="functions.html#type" title="type"><code class="xref py py-class docutils literal notranslate">builtins.type</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py data">
<dt class="sig sig-object py" id="typing.Literal">
typing.Literal<a class="headerlink" href="#typing.Literal" title="Permalink to this definition">¶</a></dt>
<dd>A type that can be used to indicate to type checkers that the
corresponding variable or function parameter has a value equivalent to
the provided literal (or one of several literals). For example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>def validate_simple(data: Any) -&gt; Literal[True]: # always returns True
 ...

MODE = Literal[&#39;r&#39;, &#39;rb&#39;, &#39;w&#39;, &#39;wb&#39;]
def open_helper(file: str, mode: MODE) -&gt; str:
 ...

open_helper(&#39;/some/path&#39;, &#39;r&#39;) # Passes type check
open_helper(&#39;/other/path&#39;, &#39;typo&#39;) # Error in type checker
</pre></div>
</div>
<code class="docutils literal notranslate">Literal[...]</code> cannot be subclassed. At runtime, an arbitrary value
is allowed as type argument to <code class="docutils literal notranslate">Literal[...]</code>, but type checkers may
impose restrictions. See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0586">PEP 586</a> for more details about literal types.
<div class="versionadded">
New in version 3.8.
</div>
<div class="versionchanged">
Changed in version 3.9.1: <code class="docutils literal notranslate">Literal</code> now de-duplicates parameters. Equality comparisons of
<code class="docutils literal notranslate">Literal</code> objects are no longer order dependent. <code class="docutils literal notranslate">Literal</code> objects
will now raise a <a class="reference internal" href="exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate">TypeError</code></a> exception during equality comparisons
if one of their parameters are not <a class="reference internal" href="../glossary.html#term-hashable">hashable</a>.
</div>
</dd></dl>

<dl class="py data">
<dt class="sig sig-object py" id="typing.ClassVar">
typing.ClassVar<a class="headerlink" href="#typing.ClassVar" title="Permalink to this definition">¶</a></dt>
<dd>Special type construct to mark class variables.
As introduced in <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0526">PEP 526</a>, a variable annotation wrapped in ClassVar
indicates that a given attribute is intended to be used as a class variable
and should not be set on instances of that class. Usage:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>class Starship:
 stats: ClassVar[dict[str, int]] = {} # class variable
 damage: int = 10 # instance variable
</pre></div>
</div>
<a class="reference internal" href="#typing.ClassVar" title="typing.ClassVar"><code class="xref py py-data docutils literal notranslate">ClassVar</code></a> accepts only types and cannot be further subscribed.
<a class="reference internal" href="#typing.ClassVar" title="typing.ClassVar"><code class="xref py py-data docutils literal notranslate">ClassVar</code></a> is not a class itself, and should not
be used with <a class="reference internal" href="functions.html#isinstance" title="isinstance"><code class="xref py py-func docutils literal notranslate">isinstance()</code></a> or <a class="reference internal" href="functions.html#issubclass" title="issubclass"><code class="xref py py-func docutils literal notranslate">issubclass()</code></a>.
<a class="reference internal" href="#typing.ClassVar" title="typing.ClassVar"><code class="xref py py-data docutils literal notranslate">ClassVar</code></a> does not change Python runtime behavior, but
it can be used by third-party type checkers. For example, a type checker
might flag the following code as an error:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>enterprise_d = Starship(3000)
enterprise_d.stats = {} # Error, setting class variable on instance
Starship.stats = {} # This is OK
</pre></div>
</div>
<div class="versionadded">
New in version 3.5.3.
</div>
</dd></dl>

<dl class="py data">
<dt class="sig sig-object py" id="typing.Final">
typing.Final<a class="headerlink" href="#typing.Final" title="Permalink to this definition">¶</a></dt>
<dd>A special typing construct to indicate to type checkers that a name
cannot be re-assigned or overridden in a subclass. For example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>MAX_SIZE: Final = 9000
MAX_SIZE += 1 # Error reported by type checker

class Connection:
 TIMEOUT: Final[int] = 10

class FastConnector(Connection):
 TIMEOUT = 1 # Error reported by type checker
</pre></div>
</div>
There is no runtime checking of these properties. See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0591">PEP 591</a> for
more details.
<div class="versionadded">
New in version 3.8.
</div>
</dd></dl>

<dl class="py data">
<dt class="sig sig-object py" id="typing.Annotated">
typing.Annotated<a class="headerlink" href="#typing.Annotated" title="Permalink to this definition">¶</a></dt>
<dd>A type, introduced in <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0593">PEP 593</a> (<code class="docutils literal notranslate">Flexible function and variable
annotations</code>), to decorate existing types with context-specific metadata
(possibly multiple pieces of it, as <code class="docutils literal notranslate">Annotated</code> is variadic).
Specifically, a type <code class="docutils literal notranslate">T</code> can be annotated with metadata <code class="docutils literal notranslate">x</code> via the
typehint <code class="docutils literal notranslate">Annotated[T, x]</code>. This metadata can be used for either static
analysis or at runtime. If a library (or tool) encounters a typehint
<code class="docutils literal notranslate">Annotated[T, x]</code> and has no special logic for metadata <code class="docutils literal notranslate">x</code>, it
should ignore it and simply treat the type as <code class="docutils literal notranslate">T</code>. Unlike the
<code class="docutils literal notranslate">no_type_check</code> functionality that currently exists in the <code class="docutils literal notranslate">typing</code>
module which completely disables typechecking annotations on a function
or a class, the <code class="docutils literal notranslate">Annotated</code> type allows for both static typechecking
of <code class="docutils literal notranslate">T</code> (which can safely ignore <code class="docutils literal notranslate">x</code>)
together with runtime access to <code class="docutils literal notranslate">x</code> within a specific application.
Ultimately, the responsibility of how to interpret the annotations (if
at all) is the responsibility of the tool or library encountering the
<code class="docutils literal notranslate">Annotated</code> type. A tool or library encountering an <code class="docutils literal notranslate">Annotated</code> type
can scan through the annotations to determine if they are of interest
(e.g., using <code class="docutils literal notranslate">isinstance()</code>).
When a tool or a library does not support annotations or encounters an
unknown annotation it should just ignore it and treat annotated type as
the underlying type.
It’s up to the tool consuming the annotations to decide whether the
client is allowed to have several annotations on one type and how to
merge those annotations.
Since the <code class="docutils literal notranslate">Annotated</code> type allows you to put several annotations of
the same (or different) type(s) on any node, the tools or libraries
consuming those annotations are in charge of dealing with potential
duplicates. For example, if you are doing value range analysis you might
allow this:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>T1 = Annotated[int, ValueRange(-10, 5)]
T2 = Annotated[T1, ValueRange(-20, 3)]
</pre></div>
</div>
Passing <code class="docutils literal notranslate">include_extras=True</code> to <a class="reference internal" href="#typing.get_type_hints" title="typing.get_type_hints"><code class="xref py py-func docutils literal notranslate">get_type_hints()</code></a> lets one
access the extra annotations at runtime.
The details of the syntax:
<ul>
<li>The first argument to <code class="docutils literal notranslate">Annotated</code> must be a valid type</li>
<li>Multiple type annotations are supported (<code class="docutils literal notranslate">Annotated</code> supports variadic
arguments):
<div class="highlight-python3 notranslate"><div class="highlight"><pre>Annotated[int, ValueRange(3, 10), ctype(&quot;char&quot;)]
</pre></div>
</div>
</li>
<li><code class="docutils literal notranslate">Annotated</code> must be called with at least two arguments (
<code class="docutils literal notranslate">Annotated[int]</code> is not valid)</li>
<li>The order of the annotations is preserved and matters for equality
checks:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>Annotated[int, ValueRange(3, 10), ctype(&quot;char&quot;)] != Annotated[
 int, ctype(&quot;char&quot;), ValueRange(3, 10)
]
</pre></div>
</div>
</li>
<li>Nested <code class="docutils literal notranslate">Annotated</code> types are flattened, with metadata ordered
starting with the innermost annotation:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>Annotated[Annotated[int, ValueRange(3, 10)], ctype(&quot;char&quot;)] == Annotated[
 int, ValueRange(3, 10), ctype(&quot;char&quot;)
]
</pre></div>
</div>
</li>
<li>Duplicated annotations are not removed:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>Annotated[int, ValueRange(3, 10)] != Annotated[
 int, ValueRange(3, 10), ValueRange(3, 10)
]
</pre></div>
</div>
</li>
<li><code class="docutils literal notranslate">Annotated</code> can be used with nested and generic aliases:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>T = TypeVar(&#39;T&#39;)
Vec = Annotated[list[tuple[T, T]], MaxLen(10)]
V = Vec[int]

V == Annotated[list[tuple[int, int]], MaxLen(10)]
</pre></div>
</div>
</li>
</ul>
<div class="versionadded">
New in version 3.9.
</div>
</dd></dl>

<dl class="py data">
<dt class="sig sig-object py" id="typing.TypeGuard">
typing.TypeGuard<a class="headerlink" href="#typing.TypeGuard" title="Permalink to this definition">¶</a></dt>
<dd>Special typing form used to annotate the return type of a user-defined
type guard function. <code class="docutils literal notranslate">TypeGuard</code> only accepts a single type argument.
At runtime, functions marked this way should return a boolean.
<code class="docutils literal notranslate">TypeGuard</code> aims to benefit type narrowing – a technique used by static
type checkers to determine a more precise type of an expression within a
program’s code flow. Usually type narrowing is done by analyzing
conditional code flow and applying the narrowing to a block of code. The
conditional expression here is sometimes referred to as a “type guard”:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>def is_str(val: str | float):
 # &quot;isinstance&quot; type guard
 if isinstance(val, str):
 # Type of ``val`` is narrowed to ``str``
 ...
 else:
 # Else, type of ``val`` is narrowed to ``float``.
 ...
</pre></div>
</div>
Sometimes it would be convenient to use a user-defined boolean function
as a type guard. Such a function should use <code class="docutils literal notranslate">TypeGuard[...]</code> as its
return type to alert static type checkers to this intention.
Using <code class="docutils literal notranslate">-&gt; TypeGuard</code> tells the static type checker that for a given
function:
<ol class="arabic simple">
<li>The return value is a boolean.</li>
<li>If the return value is <code class="docutils literal notranslate">True</code>, the type of its argument
is the type inside <code class="docutils literal notranslate">TypeGuard</code>.</li>
</ol>
For example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>def is_str_list(val: List[object]) -&gt; TypeGuard[List[str]]:
 &#39;&#39;&#39;Determines whether all objects in the list are strings&#39;&#39;&#39;
 return all(isinstance(x, str) for x in val)

def func1(val: List[object]):
 if is_str_list(val):
 # Type of ``val`` is narrowed to ``List[str]``.
 print(&quot; &quot;.join(val))
 else:
 # Type of ``val`` remains as ``List[object]``.
 print(&quot;Not a list of strings!&quot;)
</pre></div>
</div>
If <code class="docutils literal notranslate">is_str_list</code> is a class or instance method, then the type in
<code class="docutils literal notranslate">TypeGuard</code> maps to the type of the second parameter after <code class="docutils literal notranslate">cls</code> or
<code class="docutils literal notranslate">self</code>.
In short, the form <code class="docutils literal notranslate">def foo(arg: TypeA) -&gt; TypeGuard[TypeB]: ...</code>,
means that if <code class="docutils literal notranslate">foo(arg)</code> returns <code class="docutils literal notranslate">True</code>, then <code class="docutils literal notranslate">arg</code> narrows from
<code class="docutils literal notranslate">TypeA</code> to <code class="docutils literal notranslate">TypeB</code>.
<div class="admonition note">
Note
<code class="docutils literal notranslate">TypeB</code> need not be a narrower form of <code class="docutils literal notranslate">TypeA</code> – it can even be a
wider form. The main reason is to allow for things like
narrowing <code class="docutils literal notranslate">List[object]</code> to <code class="docutils literal notranslate">List[str]</code> even though the latter
is not a subtype of the former, since <code class="docutils literal notranslate">List</code> is invariant.
The responsibility of writing type-safe type guards is left to the user.
</div>
<code class="docutils literal notranslate">TypeGuard</code> also works with type variables. See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0647">PEP 647</a> for more details.
<div class="versionadded">
New in version 3.10.
</div>
</dd></dl>

</section>
<section id="building-generic-types">
<h4>Building generic types<a class="headerlink" href="#building-generic-types" title="Permalink to this headline">¶</a></h4>
These are not used in annotations. They are building blocks for creating generic types.
<dl class="py class">
<dt class="sig sig-object py" id="typing.Generic">
class typing.Generic<a class="headerlink" href="#typing.Generic" title="Permalink to this definition">¶</a></dt>
<dd>Abstract base class for generic types.
A generic type is typically declared by inheriting from an
instantiation of this class with one or more type variables.
For example, a generic mapping type might be defined as:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>class Mapping(Generic[KT, VT]):
 def __getitem__(self, key: KT) -&gt; VT:
 ...
 # Etc.
</pre></div>
</div>
This class can then be used as follows:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>X = TypeVar(&#39;X&#39;)
Y = TypeVar(&#39;Y&#39;)

def lookup_name(mapping: Mapping[X, Y], key: X, default: Y) -&gt; Y:
 try:
 return mapping[key]
 except KeyError:
 return default
</pre></div>
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.TypeVar">
class typing.TypeVar<a class="headerlink" href="#typing.TypeVar" title="Permalink to this definition">¶</a></dt>
<dd>Type variable.
Usage:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>T = TypeVar(&#39;T&#39;) # Can be anything
S = TypeVar(&#39;S&#39;, bound=str) # Can be any subtype of str
A = TypeVar(&#39;A&#39;, str, bytes) # Must be exactly str or bytes
</pre></div>
</div>
Type variables exist primarily for the benefit of static type
checkers. They serve as the parameters for generic types as well
as for generic function definitions. See <a class="reference internal" href="#typing.Generic" title="typing.Generic"><code class="xref py py-class docutils literal notranslate">Generic</code></a> for more
information on generic types. Generic functions work as follows:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>def repeat(x: T, n: int) -&gt; Sequence[T]:
 &quot;&quot;&quot;Return a list containing n references to x.&quot;&quot;&quot;
 return [x]*n

def print_capitalized(x: S) -&gt; S:
 &quot;&quot;&quot;Print x capitalized, and return x.&quot;&quot;&quot;
 print(x.capitalize())
 return x

def concatenate(x: A, y: A) -&gt; A:
 &quot;&quot;&quot;Add two strings or bytes objects together.&quot;&quot;&quot;
 return x + y
</pre></div>
</div>
Note that type variables can be bound, constrained, or neither, but
cannot be both bound and constrained.
Constrained type variables and bound type variables have different
semantics in several important ways. Using a constrained type variable
means that the <code class="docutils literal notranslate">TypeVar</code> can only ever be solved as being exactly one of
the constraints given:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>a = concatenate(&#39;one&#39;, &#39;two&#39;) # Ok, variable &#39;a&#39; has type &#39;str&#39;
b = concatenate(StringSubclass(&#39;one&#39;), StringSubclass(&#39;two&#39;)) # Inferred type of variable &#39;b&#39; is &#39;str&#39;,
 # despite &#39;StringSubclass&#39; being passed in
c = concatenate(&#39;one&#39;, b&#39;two&#39;) # error: type variable &#39;A&#39; can be either &#39;str&#39; or &#39;bytes&#39; in a function call, but not both
</pre></div>
</div>
Using a bound type variable, however, means that the <code class="docutils literal notranslate">TypeVar</code> will be
solved using the most specific type possible:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>print_capitalized(&#39;a string&#39;) # Ok, output has type &#39;str&#39;

class StringSubclass(str):
 pass

print_capitalized(StringSubclass(&#39;another string&#39;)) # Ok, output has type &#39;StringSubclass&#39;
print_capitalized(45) # error: int is not a subtype of str
</pre></div>
</div>
Type variables can be bound to concrete types, abstract types (ABCs or
protocols), and even unions of types:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>U = TypeVar(&#39;U&#39;, bound=str|bytes) # Can be any subtype of the union str|bytes
V = TypeVar(&#39;V&#39;, bound=SupportsAbs) # Can be anything with an __abs__ method
</pre></div>
</div>
Bound type variables are particularly useful for annotating
<a class="reference internal" href="functions.html#classmethod" title="classmethod"><code class="xref py py-func docutils literal notranslate">classmethods</code></a> that serve as alternative constructors.
In the following example (by
<a class="reference external" href="https://www.youtube.com/watch?v=HTLu2DFOdTg">Raymond Hettinger</a>), the
type variable <code class="docutils literal notranslate">C</code> is bound to the <code class="docutils literal notranslate">Circle</code> class through the use of a
forward reference. Using this type variable to annotate the
<code class="docutils literal notranslate">with_circumference</code> classmethod, rather than hardcoding the return type
as <code class="docutils literal notranslate">Circle</code>, means that a type checker can correctly infer the return
type even if the method is called on a subclass:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>import math

C = TypeVar(&#39;C&#39;, bound=&#39;Circle&#39;)

class Circle:
 &quot;&quot;&quot;An abstract circle&quot;&quot;&quot;

def __init__(self, radius: float) -&gt; None:
 self.radius = radius

# Use a type variable to show that the return type
 # will always be an instance of whatever ``cls`` is
 @classmethod
 def with_circumference(cls: type[C], circumference: float) -&gt; C:
 &quot;&quot;&quot;Create a circle with the specified circumference&quot;&quot;&quot;
 radius = circumference / (math.pi * 2)
 return cls(radius)

class Tire(Circle):
 &quot;&quot;&quot;A specialised circle (made out of rubber)&quot;&quot;&quot;

MATERIAL = &#39;rubber&#39;

c = Circle.with_circumference(3) # Ok, variable &#39;c&#39; has type &#39;Circle&#39;
t = Tire.with_circumference(4) # Ok, variable &#39;t&#39; has type &#39;Tire&#39; (not &#39;Circle&#39;)
</pre></div>
</div>
At runtime, <code class="docutils literal notranslate">isinstance(x, T)</code> will raise <a class="reference internal" href="exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate">TypeError</code></a>. In general,
<a class="reference internal" href="functions.html#isinstance" title="isinstance"><code class="xref py py-func docutils literal notranslate">isinstance()</code></a> and <a class="reference internal" href="functions.html#issubclass" title="issubclass"><code class="xref py py-func docutils literal notranslate">issubclass()</code></a> should not be used with types.
Type variables may be marked covariant or contravariant by passing
<code class="docutils literal notranslate">covariant=True</code> or <code class="docutils literal notranslate">contravariant=True</code>. See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0484">PEP 484</a> for more
details. By default, type variables are invariant.
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.ParamSpec">
class typing.ParamSpec(name, *, bound=None, covariant=False, contravariant=False)<a class="headerlink" href="#typing.ParamSpec" title="Permalink to this definition">¶</a></dt>
<dd>Parameter specification variable. A specialized version of
<a class="reference internal" href="#typing.TypeVar" title="typing.TypeVar"><code class="xref py py-class docutils literal notranslate">type variables</code></a>.
Usage:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>P = ParamSpec(&#39;P&#39;)
</pre></div>
</div>
Parameter specification variables exist primarily for the benefit of static
type checkers. They are used to forward the parameter types of one
callable to another callable – a pattern commonly found in higher order
functions and decorators. They are only valid when used in <code class="docutils literal notranslate">Concatenate</code>,
or as the first argument to <code class="docutils literal notranslate">Callable</code>, or as parameters for user-defined
Generics. See <a class="reference internal" href="#typing.Generic" title="typing.Generic"><code class="xref py py-class docutils literal notranslate">Generic</code></a> for more information on generic types.
For example, to add basic logging to a function, one can create a decorator
<code class="docutils literal notranslate">add_logging</code> to log function calls. The parameter specification variable
tells the type checker that the callable passed into the decorator and the
new callable returned by it have inter-dependent type parameters:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>from collections.abc import Callable
from typing import TypeVar, ParamSpec
import logging

def add_logging(f: Callable[P, T]) -&gt; Callable[P, T]:
 &#39;&#39;&#39;A type-safe decorator to add logging to a function.&#39;&#39;&#39;
 def inner(*args: P.args, **kwargs: P.kwargs) -&gt; T:
 logging.info(f&#39;{f.__name__} was called&#39;)
 return f(*args, **kwargs)
 return inner

@add_logging
def add_two(x: float, y: float) -&gt; float:
 &#39;&#39;&#39;Add two numbers together.&#39;&#39;&#39;
 return x + y
</pre></div>
</div>
Without <code class="docutils literal notranslate">ParamSpec</code>, the simplest way to annotate this previously was to
use a <a class="reference internal" href="#typing.TypeVar" title="typing.TypeVar"><code class="xref py py-class docutils literal notranslate">TypeVar</code></a> with bound <code class="docutils literal notranslate">Callable[..., Any]</code>. However this
causes two problems:
<ol class="arabic simple">
<li>The type checker can’t type check the <code class="docutils literal notranslate">inner</code> function because
<code class="docutils literal notranslate">*args</code> and <code class="docutils literal notranslate">**kwargs</code> have to be typed <a class="reference internal" href="#typing.Any" title="typing.Any"><code class="xref py py-data docutils literal notranslate">Any</code></a>.</li>
<li><a class="reference internal" href="#typing.cast" title="typing.cast"><code class="xref py py-func docutils literal notranslate">cast()</code></a> may be required in the body of the <code class="docutils literal notranslate">add_logging</code>
decorator when returning the <code class="docutils literal notranslate">inner</code> function, or the static type
checker must be told to ignore the <code class="docutils literal notranslate">return inner</code>.</li>
</ol>
<dl class="py attribute">
<dt class="sig sig-object py" id="typing.ParamSpec.args">
args<a class="headerlink" href="#typing.ParamSpec.args" title="Permalink to this definition">¶</a></dt>
<dd></dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="typing.ParamSpec.kwargs">
kwargs<a class="headerlink" href="#typing.ParamSpec.kwargs" title="Permalink to this definition">¶</a></dt>
<dd>Since <code class="docutils literal notranslate">ParamSpec</code> captures both positional and keyword parameters,
<code class="docutils literal notranslate">P.args</code> and <code class="docutils literal notranslate">P.kwargs</code> can be used to split a <code class="docutils literal notranslate">ParamSpec</code> into its
components. <code class="docutils literal notranslate">P.args</code> represents the tuple of positional parameters in a
given call and should only be used to annotate <code class="docutils literal notranslate">*args</code>. <code class="docutils literal notranslate">P.kwargs</code>
represents the mapping of keyword parameters to their values in a given call,
and should be only be used to annotate <code class="docutils literal notranslate">**kwargs</code>. Both
attributes require the annotated parameter to be in scope. At runtime,
<code class="docutils literal notranslate">P.args</code> and <code class="docutils literal notranslate">P.kwargs</code> are instances respectively of
<a class="reference internal" href="#typing.ParamSpecArgs" title="typing.ParamSpecArgs"><code class="xref py py-class docutils literal notranslate">ParamSpecArgs</code></a> and <a class="reference internal" href="#typing.ParamSpecKwargs" title="typing.ParamSpecKwargs"><code class="xref py py-class docutils literal notranslate">ParamSpecKwargs</code></a>.
</dd></dl>

Parameter specification variables created with <code class="docutils literal notranslate">covariant=True</code> or
<code class="docutils literal notranslate">contravariant=True</code> can be used to declare covariant or contravariant
generic types. The <code class="docutils literal notranslate">bound</code> argument is also accepted, similar to
<a class="reference internal" href="#typing.TypeVar" title="typing.TypeVar"><code class="xref py py-class docutils literal notranslate">TypeVar</code></a>. However the actual semantics of these keywords are yet to
be decided.
<div class="versionadded">
New in version 3.10.
</div>
<div class="admonition note">
Note
Only parameter specification variables defined in global scope can
be pickled.
</div>
<div class="admonition seealso">
See also
<ul class="simple">
<li><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0612">PEP 612</a> – Parameter Specification Variables (the PEP which introduced
<code class="docutils literal notranslate">ParamSpec</code> and <code class="docutils literal notranslate">Concatenate</code>).</li>
<li><a class="reference internal" href="#typing.Callable" title="typing.Callable"><code class="xref py py-class docutils literal notranslate">Callable</code></a> and <a class="reference internal" href="#typing.Concatenate" title="typing.Concatenate"><code class="xref py py-class docutils literal notranslate">Concatenate</code></a>.</li>
</ul>
</div>
</dd></dl>

<dl class="py data">
<dt class="sig sig-object py" id="typing.ParamSpecArgs">
typing.ParamSpecArgs<a class="headerlink" href="#typing.ParamSpecArgs" title="Permalink to this definition">¶</a></dt>
<dd></dd></dl>

<dl class="py data">
<dt class="sig sig-object py" id="typing.ParamSpecKwargs">
typing.ParamSpecKwargs<a class="headerlink" href="#typing.ParamSpecKwargs" title="Permalink to this definition">¶</a></dt>
<dd>Arguments and keyword arguments attributes of a <a class="reference internal" href="#typing.ParamSpec" title="typing.ParamSpec"><code class="xref py py-class docutils literal notranslate">ParamSpec</code></a>. The
<code class="docutils literal notranslate">P.args</code> attribute of a <code class="docutils literal notranslate">ParamSpec</code> is an instance of <code class="docutils literal notranslate">ParamSpecArgs</code>,
and <code class="docutils literal notranslate">P.kwargs</code> is an instance of <code class="docutils literal notranslate">ParamSpecKwargs</code>. They are intended
for runtime introspection and have no special meaning to static type checkers.
Calling <a class="reference internal" href="#typing.get_origin" title="typing.get_origin"><code class="xref py py-func docutils literal notranslate">get_origin()</code></a> on either of these objects will return the
original <code class="docutils literal notranslate">ParamSpec</code>:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>P = ParamSpec(&quot;P&quot;)
get_origin(P.args) # returns P
get_origin(P.kwargs) # returns P
</pre></div>
</div>
<div class="versionadded">
New in version 3.10.
</div>
</dd></dl>

<dl class="py data">
<dt class="sig sig-object py" id="typing.AnyStr">
typing.AnyStr<a class="headerlink" href="#typing.AnyStr" title="Permalink to this definition">¶</a></dt>
<dd><code class="docutils literal notranslate">AnyStr</code> is a <a class="reference internal" href="#typing.TypeVar" title="typing.TypeVar"><code class="xref py py-class docutils literal notranslate">constrained type variable</code></a> defined as
<code class="docutils literal notranslate">AnyStr = TypeVar('AnyStr', str, bytes)</code>.
It is meant to be used for functions that may accept any kind of string
without allowing different kinds of strings to mix. For example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>def concat(a: AnyStr, b: AnyStr) -&gt; AnyStr:
 return a + b

concat(u&quot;foo&quot;, u&quot;bar&quot;) # Ok, output has type &#39;unicode&#39;
concat(b&quot;foo&quot;, b&quot;bar&quot;) # Ok, output has type &#39;bytes&#39;
concat(u&quot;foo&quot;, b&quot;bar&quot;) # Error, cannot mix unicode and bytes
</pre></div>
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.Protocol">
class typing.Protocol(Generic)<a class="headerlink" href="#typing.Protocol" title="Permalink to this definition">¶</a></dt>
<dd>Base class for protocol classes. Protocol classes are defined like this:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>class Proto(Protocol):
 def meth(self) -&gt; int:
 ...
</pre></div>
</div>
Such classes are primarily used with static type checkers that recognize
structural subtyping (static duck-typing), for example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>class C:
 def meth(self) -&gt; int:
 return 0

def func(x: Proto) -&gt; int:
 return x.meth()

func(C()) # Passes static type check
</pre></div>
</div>
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0544">PEP 544</a> for more details. Protocol classes decorated with
<a class="reference internal" href="#typing.runtime_checkable" title="typing.runtime_checkable"><code class="xref py py-func docutils literal notranslate">runtime_checkable()</code></a> (described later) act as simple-minded runtime
protocols that check only the presence of given attributes, ignoring their
type signatures.
Protocol classes can be generic, for example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>class GenProto(Protocol[T]):
 def meth(self) -&gt; T:
 ...
</pre></div>
</div>
<div class="versionadded">
New in version 3.8.
</div>
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="typing.runtime_checkable">
&#64;typing.runtime_checkable<a class="headerlink" href="#typing.runtime_checkable" title="Permalink to this definition">¶</a></dt>
<dd>Mark a protocol class as a runtime protocol.
Such a protocol can be used with <a class="reference internal" href="functions.html#isinstance" title="isinstance"><code class="xref py py-func docutils literal notranslate">isinstance()</code></a> and <a class="reference internal" href="functions.html#issubclass" title="issubclass"><code class="xref py py-func docutils literal notranslate">issubclass()</code></a>.
This raises <a class="reference internal" href="exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate">TypeError</code></a> when applied to a non-protocol class. This
allows a simple-minded structural check, very similar to “one trick ponies”
in <a class="reference internal" href="collections.abc.html#module-collections.abc" title="collections.abc: Abstract base classes for containers"><code class="xref py py-mod docutils literal notranslate">collections.abc</code></a> such as <a class="reference internal" href="collections.abc.html#collections.abc.Iterable" title="collections.abc.Iterable"><code class="xref py py-class docutils literal notranslate">Iterable</code></a>. For example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>@runtime_checkable
class Closable(Protocol):
 def close(self): ...

assert isinstance(open(&#39;/some/file&#39;), Closable)

@runtime_checkable
class Named(Protocol):
 name: str

import threading
assert isinstance(threading.Thread(name=&#39;Bob&#39;), Named)
</pre></div>
</div>
<div class="admonition note">
Note
<code class="xref py py-func docutils literal notranslate">runtime_checkable()</code> will check only the presence of the required
methods or attributes, not their type signatures or types.
For example, <a class="reference internal" href="ssl.html#ssl.SSLObject" title="ssl.SSLObject"><code class="xref py py-class docutils literal notranslate">ssl.SSLObject</code></a>
is a class, therefore it passes an <a class="reference internal" href="functions.html#issubclass" title="issubclass"><code class="xref py py-func docutils literal notranslate">issubclass()</code></a>
check against <a class="reference internal" href="#typing.Callable" title="typing.Callable"><code class="xref py py-data docutils literal notranslate">Callable</code></a>. However, the
<code class="docutils literal notranslate">ssl.SSLObject.__init__</code> method exists only to raise a
<a class="reference internal" href="exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate">TypeError</code></a> with a more informative message, therefore making
it impossible to call (instantiate) <a class="reference internal" href="ssl.html#ssl.SSLObject" title="ssl.SSLObject"><code class="xref py py-class docutils literal notranslate">ssl.SSLObject</code></a>.
</div>
<div class="admonition note">
Note
An <a class="reference internal" href="functions.html#isinstance" title="isinstance"><code class="xref py py-func docutils literal notranslate">isinstance()</code></a> check against a runtime-checkable protocol can be
surprisingly slow compared to an <code class="docutils literal notranslate">isinstance()</code> check against
a non-protocol class. Consider using alternative idioms such as
<a class="reference internal" href="functions.html#hasattr" title="hasattr"><code class="xref py py-func docutils literal notranslate">hasattr()</code></a> calls for structural checks in performance-sensitive
code.
</div>
<div class="versionadded">
New in version 3.8.
</div>
</dd></dl>

</section>
<section id="other-special-directives">
<h4>Other special directives<a class="headerlink" href="#other-special-directives" title="Permalink to this headline">¶</a></h4>
These are not used in annotations. They are building blocks for declaring types.
<dl class="py class">
<dt class="sig sig-object py" id="typing.NamedTuple">
class typing.NamedTuple<a class="headerlink" href="#typing.NamedTuple" title="Permalink to this definition">¶</a></dt>
<dd>Typed version of <a class="reference internal" href="collections.html#collections.namedtuple" title="collections.namedtuple"><code class="xref py py-func docutils literal notranslate">collections.namedtuple()</code></a>.
Usage:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>class Employee(NamedTuple):
 name: str
 id: int
</pre></div>
</div>
This is equivalent to:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>Employee = collections.namedtuple(&#39;Employee&#39;, [&#39;name&#39;, &#39;id&#39;])
</pre></div>
</div>
To give a field a default value, you can assign to it in the class body:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>class Employee(NamedTuple):
 name: str
 id: int = 3

employee = Employee(&#39;Guido&#39;)
assert employee.id == 3
</pre></div>
</div>
Fields with a default value must come after any fields without a default.
The resulting class has an extra attribute <code class="docutils literal notranslate">__annotations__</code> giving a
dict that maps the field names to the field types. (The field names are in
the <code class="docutils literal notranslate">_fields</code> attribute and the default values are in the
<code class="docutils literal notranslate">_field_defaults</code> attribute, both of which are part of the <a class="reference internal" href="collections.html#collections.namedtuple" title="collections.namedtuple"><code class="xref py py-func docutils literal notranslate">namedtuple()</code></a>
API.)
<code class="docutils literal notranslate">NamedTuple</code> subclasses can also have docstrings and methods:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>class Employee(NamedTuple):
 &quot;&quot;&quot;Represents an employee.&quot;&quot;&quot;
 name: str
 id: int = 3

def __repr__(self) -&gt; str:
 return f&#39;&lt;Employee {self.name}, id={self.id}&gt;&#39;
</pre></div>
</div>
Backward-compatible usage:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>Employee = NamedTuple(&#39;Employee&#39;, [(&#39;name&#39;, str), (&#39;id&#39;, int)])
</pre></div>
</div>
<div class="versionchanged">
Changed in version 3.6: Added support for <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0526">PEP 526</a> variable annotation syntax.
</div>
<div class="versionchanged">
Changed in version 3.6.1: Added support for default values, methods, and docstrings.
</div>
<div class="versionchanged">
Changed in version 3.8: The <code class="docutils literal notranslate">_field_types</code> and <code class="docutils literal notranslate">__annotations__</code> attributes are
now regular dictionaries instead of instances of <code class="docutils literal notranslate">OrderedDict</code>.
</div>
<div class="versionchanged">
Changed in version 3.9: Removed the <code class="docutils literal notranslate">_field_types</code> attribute in favor of the more
standard <code class="docutils literal notranslate">__annotations__</code> attribute which has the same information.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.NewType">
class typing.NewType(name, tp)<a class="headerlink" href="#typing.NewType" title="Permalink to this definition">¶</a></dt>
<dd>A helper class to indicate a distinct type to a typechecker,
see <a class="reference internal" href="#distinct">NewType</a>. At runtime it returns an object that returns
its argument when called.
Usage:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>UserId = NewType(&#39;UserId&#39;, int)
first_user = UserId(1)
</pre></div>
</div>
<div class="versionadded">
New in version 3.5.2.
</div>
<div class="versionchanged">
Changed in version 3.10: <code class="docutils literal notranslate">NewType</code> is now a class rather than a function.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.TypedDict">
class typing.TypedDict(dict)<a class="headerlink" href="#typing.TypedDict" title="Permalink to this definition">¶</a></dt>
<dd>Special construct to add type hints to a dictionary.
At runtime it is a plain <a class="reference internal" href="stdtypes.html#dict" title="dict"><code class="xref py py-class docutils literal notranslate">dict</code></a>.
<code class="docutils literal notranslate">TypedDict</code> declares a dictionary type that expects all of its
instances to have a certain set of keys, where each key is
associated with a value of a consistent type. This expectation
is not checked at runtime but is only enforced by type checkers.
Usage:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>class Point2D(TypedDict):
 x: int
 y: int
 label: str

a: Point2D = {&#39;x&#39;: 1, &#39;y&#39;: 2, &#39;label&#39;: &#39;good&#39;} # OK
b: Point2D = {&#39;z&#39;: 3, &#39;label&#39;: &#39;bad&#39;} # Fails type check

assert Point2D(x=1, y=2, label=&#39;first&#39;) == dict(x=1, y=2, label=&#39;first&#39;)
</pre></div>
</div>
To allow using this feature with older versions of Python that do not
support <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0526">PEP 526</a>, <code class="docutils literal notranslate">TypedDict</code> supports two additional equivalent
syntactic forms:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>Point2D = TypedDict(&#39;Point2D&#39;, x=int, y=int, label=str)
Point2D = TypedDict(&#39;Point2D&#39;, {&#39;x&#39;: int, &#39;y&#39;: int, &#39;label&#39;: str})
</pre></div>
</div>
The functional syntax should also be used when any of the keys are not valid
<a class="reference internal" href="../reference/lexical_analysis.html#identifiers">identifiers</a>, for example because they are keywords or contain hyphens.
Example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre># raises SyntaxError
class Point2D(TypedDict):
 in: int # &#39;in&#39; is a keyword
 x-y: int # name with hyphens

# OK, functional syntax
Point2D = TypedDict(&#39;Point2D&#39;, {&#39;in&#39;: int, &#39;x-y&#39;: int})
</pre></div>
</div>
By default, all keys must be present in a <code class="docutils literal notranslate">TypedDict</code>. It is possible to
override this by specifying totality.
Usage:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>class Point2D(TypedDict, total=False):
 x: int
 y: int
</pre></div>
</div>
This means that a <code class="docutils literal notranslate">Point2D</code> <code class="docutils literal notranslate">TypedDict</code> can have any of the keys
omitted. A type checker is only expected to support a literal <code class="docutils literal notranslate">False</code> or
<code class="docutils literal notranslate">True</code> as the value of the <code class="docutils literal notranslate">total</code> argument. <code class="docutils literal notranslate">True</code> is the default,
and makes all items defined in the class body required.
It is possible for a <code class="docutils literal notranslate">TypedDict</code> type to inherit from one or more other <code class="docutils literal notranslate">TypedDict</code> types
using the class-based syntax.
Usage:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>class Point3D(Point2D):
 z: int
</pre></div>
</div>
<code class="docutils literal notranslate">Point3D</code> has three items: <code class="docutils literal notranslate">x</code>, <code class="docutils literal notranslate">y</code> and <code class="docutils literal notranslate">z</code>. It is equivalent to this
definition:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>class Point3D(TypedDict):
 x: int
 y: int
 z: int
</pre></div>
</div>
A <code class="docutils literal notranslate">TypedDict</code> cannot inherit from a non-<code class="docutils literal notranslate">TypedDict</code> class,
notably including <a class="reference internal" href="#typing.Generic" title="typing.Generic"><code class="xref py py-class docutils literal notranslate">Generic</code></a>. For example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>class X(TypedDict):
 x: int

class Y(TypedDict):
 y: int

class Z(object): pass # A non-TypedDict class

class XY(X, Y): pass # OK

class XZ(X, Z): pass # raises TypeError

T = TypeVar(&#39;T&#39;)
class XT(X, Generic[T]): pass # raises TypeError
</pre></div>
</div>
A <code class="docutils literal notranslate">TypedDict</code> can be introspected via annotations dicts
(see <a class="reference internal" href="../howto/annotations.html#annotations-howto">Annotations Best Practices</a> for more information on annotations best practices),
<a class="reference internal" href="#typing.TypedDict.__total__" title="typing.TypedDict.__total__"><code class="xref py py-attr docutils literal notranslate">__total__</code></a>, <a class="reference internal" href="#typing.TypedDict.__required_keys__" title="typing.TypedDict.__required_keys__"><code class="xref py py-attr docutils literal notranslate">__required_keys__</code></a>, and <a class="reference internal" href="#typing.TypedDict.__optional_keys__" title="typing.TypedDict.__optional_keys__"><code class="xref py py-attr docutils literal notranslate">__optional_keys__</code></a>.
<dl class="py attribute">
<dt class="sig sig-object py" id="typing.TypedDict.__total__">
__total__<a class="headerlink" href="#typing.TypedDict.__total__" title="Permalink to this definition">¶</a></dt>
<dd><code class="docutils literal notranslate">Point2D.__total__</code> gives the value of the <code class="docutils literal notranslate">total</code> argument.
Example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; from typing import TypedDict
&gt;&gt;&gt; class Point2D(TypedDict): pass
&gt;&gt;&gt; Point2D.__total__
True
&gt;&gt;&gt; class Point2D(TypedDict, total=False): pass
&gt;&gt;&gt; Point2D.__total__
False
&gt;&gt;&gt; class Point3D(Point2D): pass
&gt;&gt;&gt; Point3D.__total__
True
</pre></div>
</div>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="typing.TypedDict.__required_keys__">
__required_keys__<a class="headerlink" href="#typing.TypedDict.__required_keys__" title="Permalink to this definition">¶</a></dt>
<dd><div class="versionadded">
New in version 3.9.
</div>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="typing.TypedDict.__optional_keys__">
__optional_keys__<a class="headerlink" href="#typing.TypedDict.__optional_keys__" title="Permalink to this definition">¶</a></dt>
<dd><code class="docutils literal notranslate">Point2D.__required_keys__</code> and <code class="docutils literal notranslate">Point2D.__optional_keys__</code> return
<a class="reference internal" href="stdtypes.html#frozenset" title="frozenset"><code class="xref py py-class docutils literal notranslate">frozenset</code></a> objects containing required and non-required keys, respectively.
Currently the only way to declare both required and non-required keys in the
same <code class="docutils literal notranslate">TypedDict</code> is mixed inheritance, declaring a <code class="docutils literal notranslate">TypedDict</code> with one value
for the <code class="docutils literal notranslate">total</code> argument and then inheriting it from another <code class="docutils literal notranslate">TypedDict</code> with
a different value for <code class="docutils literal notranslate">total</code>.
Usage:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; class Point2D(TypedDict, total=False):
... x: int
... y: int
...
&gt;&gt;&gt; class Point3D(Point2D):
... z: int
...
&gt;&gt;&gt; Point3D.__required_keys__ == frozenset({&#39;z&#39;})
True
&gt;&gt;&gt; Point3D.__optional_keys__ == frozenset({&#39;x&#39;, &#39;y&#39;})
True
</pre></div>
</div>
<div class="versionadded">
New in version 3.9.
</div>
</dd></dl>

See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0589">PEP 589</a> for more examples and detailed rules of using <code class="docutils literal notranslate">TypedDict</code>.
<div class="versionadded">
New in version 3.8.
</div>
</dd></dl>

</section>
</section>
<section id="generic-concrete-collections">
<h3>Generic concrete collections<a class="headerlink" href="#generic-concrete-collections" title="Permalink to this headline">¶</a></h3>
<section id="corresponding-to-built-in-types">
<h4>Corresponding to built-in types<a class="headerlink" href="#corresponding-to-built-in-types" title="Permalink to this headline">¶</a></h4>
<dl class="py class">
<dt class="sig sig-object py" id="typing.Dict">
class typing.Dict(dict, MutableMapping[KT, VT])<a class="headerlink" href="#typing.Dict" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="stdtypes.html#dict" title="dict"><code class="xref py py-class docutils literal notranslate">dict</code></a>.
Useful for annotating return types. To annotate arguments it is preferred
to use an abstract collection type such as <a class="reference internal" href="#typing.Mapping" title="typing.Mapping"><code class="xref py py-class docutils literal notranslate">Mapping</code></a>.
This type can be used as follows:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>def count_words(text: str) -&gt; Dict[str, int]:
 ...
</pre></div>
</div>
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="stdtypes.html#dict" title="dict"><code class="xref py py-class docutils literal notranslate">builtins.dict</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.List">
class typing.List(list, MutableSequence[T])<a class="headerlink" href="#typing.List" title="Permalink to this definition">¶</a></dt>
<dd>Generic version of <a class="reference internal" href="stdtypes.html#list" title="list"><code class="xref py py-class docutils literal notranslate">list</code></a>.
Useful for annotating return types. To annotate arguments it is preferred
to use an abstract collection type such as <a class="reference internal" href="#typing.Sequence" title="typing.Sequence"><code class="xref py py-class docutils literal notranslate">Sequence</code></a> or
<a class="reference internal" href="#typing.Iterable" title="typing.Iterable"><code class="xref py py-class docutils literal notranslate">Iterable</code></a>.
This type may be used as follows:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>T = TypeVar(&#39;T&#39;, int, float)

def vec2(x: T, y: T) -&gt; List[T]:
 return [x, y]

def keep_positives(vector: Sequence[T]) -&gt; List[T]:
 return [item for item in vector if item &gt; 0]
</pre></div>
</div>
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="stdtypes.html#list" title="list"><code class="xref py py-class docutils literal notranslate">builtins.list</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.Set">
class typing.Set(set, MutableSet[T])<a class="headerlink" href="#typing.Set" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="stdtypes.html#set" title="set"><code class="xref py py-class docutils literal notranslate">builtins.set</code></a>.
Useful for annotating return types. To annotate arguments it is preferred
to use an abstract collection type such as <a class="reference internal" href="#typing.AbstractSet" title="typing.AbstractSet"><code class="xref py py-class docutils literal notranslate">AbstractSet</code></a>.
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="stdtypes.html#set" title="set"><code class="xref py py-class docutils literal notranslate">builtins.set</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.FrozenSet">
class typing.FrozenSet(frozenset, AbstractSet[T_co])<a class="headerlink" href="#typing.FrozenSet" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="stdtypes.html#frozenset" title="frozenset"><code class="xref py py-class docutils literal notranslate">builtins.frozenset</code></a>.
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="stdtypes.html#frozenset" title="frozenset"><code class="xref py py-class docutils literal notranslate">builtins.frozenset</code></a>
now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<div class="admonition note">
Note
<a class="reference internal" href="#typing.Tuple" title="typing.Tuple"><code class="xref py py-data docutils literal notranslate">Tuple</code></a> is a special form.
</div>
</section>
<section id="corresponding-to-types-in-collections">
<h4>Corresponding to types in <a class="reference internal" href="collections.html#module-collections" title="collections: Container datatypes"><code class="xref py py-mod docutils literal notranslate">collections</code></a><a class="headerlink" href="#corresponding-to-types-in-collections" title="Permalink to this headline">¶</a></h4>
<dl class="py class">
<dt class="sig sig-object py" id="typing.DefaultDict">
class typing.DefaultDict(collections.defaultdict, MutableMapping[KT, VT])<a class="headerlink" href="#typing.DefaultDict" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="collections.html#collections.defaultdict" title="collections.defaultdict"><code class="xref py py-class docutils literal notranslate">collections.defaultdict</code></a>.
<div class="versionadded">
New in version 3.5.2.
</div>
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="collections.html#collections.defaultdict" title="collections.defaultdict"><code class="xref py py-class docutils literal notranslate">collections.defaultdict</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.OrderedDict">
class typing.OrderedDict(collections.OrderedDict, MutableMapping[KT, VT])<a class="headerlink" href="#typing.OrderedDict" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="collections.html#collections.OrderedDict" title="collections.OrderedDict"><code class="xref py py-class docutils literal notranslate">collections.OrderedDict</code></a>.
<div class="versionadded">
New in version 3.7.2.
</div>
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="collections.html#collections.OrderedDict" title="collections.OrderedDict"><code class="xref py py-class docutils literal notranslate">collections.OrderedDict</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.ChainMap">
class typing.ChainMap(collections.ChainMap, MutableMapping[KT, VT])<a class="headerlink" href="#typing.ChainMap" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="collections.html#collections.ChainMap" title="collections.ChainMap"><code class="xref py py-class docutils literal notranslate">collections.ChainMap</code></a>.
<div class="versionadded">
New in version 3.5.4.
</div>
<div class="versionadded">
New in version 3.6.1.
</div>
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="collections.html#collections.ChainMap" title="collections.ChainMap"><code class="xref py py-class docutils literal notranslate">collections.ChainMap</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.Counter">
class typing.Counter(collections.Counter, Dict[T, int])<a class="headerlink" href="#typing.Counter" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="collections.html#collections.Counter" title="collections.Counter"><code class="xref py py-class docutils literal notranslate">collections.Counter</code></a>.
<div class="versionadded">
New in version 3.5.4.
</div>
<div class="versionadded">
New in version 3.6.1.
</div>
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="collections.html#collections.Counter" title="collections.Counter"><code class="xref py py-class docutils literal notranslate">collections.Counter</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.Deque">
class typing.Deque(deque, MutableSequence[T])<a class="headerlink" href="#typing.Deque" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="collections.html#collections.deque" title="collections.deque"><code class="xref py py-class docutils literal notranslate">collections.deque</code></a>.
<div class="versionadded">
New in version 3.5.4.
</div>
<div class="versionadded">
New in version 3.6.1.
</div>
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="collections.html#collections.deque" title="collections.deque"><code class="xref py py-class docutils literal notranslate">collections.deque</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

</section>
<section id="other-concrete-types">
<h4>Other concrete types<a class="headerlink" href="#other-concrete-types" title="Permalink to this headline">¶</a></h4>
<dl class="py class">
<dt class="sig sig-object py" id="typing.IO">
class typing.IO<a class="headerlink" href="#typing.IO" title="Permalink to this definition">¶</a></dt>
<dt class="sig sig-object py" id="typing.TextIO">
class typing.TextIO<a class="headerlink" href="#typing.TextIO" title="Permalink to this definition">¶</a></dt>
<dt class="sig sig-object py" id="typing.BinaryIO">
class typing.BinaryIO<a class="headerlink" href="#typing.BinaryIO" title="Permalink to this definition">¶</a></dt>
<dd>Generic type <code class="docutils literal notranslate">IO[AnyStr]</code> and its subclasses <code class="docutils literal notranslate">TextIO(IO[str])</code>
and <code class="docutils literal notranslate">BinaryIO(IO[bytes])</code>
represent the types of I/O streams such as returned by
<a class="reference internal" href="functions.html#open" title="open"><code class="xref py py-func docutils literal notranslate">open()</code></a>.
<div class="deprecated-removed">
Deprecated since version 3.8, will be removed in version 3.13: The <code class="docutils literal notranslate">typing.io</code> namespace is deprecated and will be removed.
These types should be directly imported from <code class="docutils literal notranslate">typing</code> instead.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.Pattern">
class typing.Pattern<a class="headerlink" href="#typing.Pattern" title="Permalink to this definition">¶</a></dt>
<dt class="sig sig-object py" id="typing.Match">
class typing.Match<a class="headerlink" href="#typing.Match" title="Permalink to this definition">¶</a></dt>
<dd>These type aliases
correspond to the return types from <a class="reference internal" href="re.html#re.compile" title="re.compile"><code class="xref py py-func docutils literal notranslate">re.compile()</code></a> and
<a class="reference internal" href="re.html#re.match" title="re.match"><code class="xref py py-func docutils literal notranslate">re.match()</code></a>. These types (and the corresponding functions)
are generic in <code class="docutils literal notranslate">AnyStr</code> and can be made specific by writing
<code class="docutils literal notranslate">Pattern[str]</code>, <code class="docutils literal notranslate">Pattern[bytes]</code>, <code class="docutils literal notranslate">Match[str]</code>, or
<code class="docutils literal notranslate">Match[bytes]</code>.
<div class="deprecated-removed">
Deprecated since version 3.8, will be removed in version 3.13: The <code class="docutils literal notranslate">typing.re</code> namespace is deprecated and will be removed.
These types should be directly imported from <code class="docutils literal notranslate">typing</code> instead.
</div>
<div class="deprecated">
Deprecated since version 3.9: Classes <code class="docutils literal notranslate">Pattern</code> and <code class="docutils literal notranslate">Match</code> from <a class="reference internal" href="re.html#module-re" title="re: Regular expression operations."><code class="xref py py-mod docutils literal notranslate">re</code></a> now support <code class="docutils literal notranslate">[]</code>.
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.Text">
class typing.Text<a class="headerlink" href="#typing.Text" title="Permalink to this definition">¶</a></dt>
<dd><code class="docutils literal notranslate">Text</code> is an alias for <code class="docutils literal notranslate">str</code>. It is provided to supply a forward
compatible path for Python 2 code: in Python 2, <code class="docutils literal notranslate">Text</code> is an alias for
<code class="docutils literal notranslate">unicode</code>.
Use <code class="docutils literal notranslate">Text</code> to indicate that a value must contain a unicode string in
a manner that is compatible with both Python 2 and Python 3:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>def add_unicode_checkmark(text: Text) -&gt; Text:
 return text + u&#39; \u2713&#39;
</pre></div>
</div>
<div class="versionadded">
New in version 3.5.2.
</div>
</dd></dl>

</section>
</section>
<section id="abstract-base-classes">
<h3>Abstract Base Classes<a class="headerlink" href="#abstract-base-classes" title="Permalink to this headline">¶</a></h3>
<section id="corresponding-to-collections-in-collections-abc">
<h4>Corresponding to collections in <a class="reference internal" href="collections.abc.html#module-collections.abc" title="collections.abc: Abstract base classes for containers"><code class="xref py py-mod docutils literal notranslate">collections.abc</code></a><a class="headerlink" href="#corresponding-to-collections-in-collections-abc" title="Permalink to this headline">¶</a></h4>
<dl class="py class">
<dt class="sig sig-object py" id="typing.AbstractSet">
class typing.AbstractSet(Collection[T_co])<a class="headerlink" href="#typing.AbstractSet" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="collections.abc.html#collections.abc.Set" title="collections.abc.Set"><code class="xref py py-class docutils literal notranslate">collections.abc.Set</code></a>.
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="collections.abc.html#collections.abc.Set" title="collections.abc.Set"><code class="xref py py-class docutils literal notranslate">collections.abc.Set</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.ByteString">
class typing.ByteString(Sequence[int])<a class="headerlink" href="#typing.ByteString" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="collections.abc.html#collections.abc.ByteString" title="collections.abc.ByteString"><code class="xref py py-class docutils literal notranslate">collections.abc.ByteString</code></a>.
This type represents the types <a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a>, <a class="reference internal" href="stdtypes.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate">bytearray</code></a>,
and <a class="reference internal" href="stdtypes.html#memoryview" title="memoryview"><code class="xref py py-class docutils literal notranslate">memoryview</code></a> of byte sequences.
As a shorthand for this type, <a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a> can be used to
annotate arguments of any of the types mentioned above.
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="collections.abc.html#collections.abc.ByteString" title="collections.abc.ByteString"><code class="xref py py-class docutils literal notranslate">collections.abc.ByteString</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.Collection">
class typing.Collection(Sized, Iterable[T_co], Container[T_co])<a class="headerlink" href="#typing.Collection" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="collections.abc.html#collections.abc.Collection" title="collections.abc.Collection"><code class="xref py py-class docutils literal notranslate">collections.abc.Collection</code></a>
<div class="versionadded">
New in version 3.6.0.
</div>
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="collections.abc.html#collections.abc.Collection" title="collections.abc.Collection"><code class="xref py py-class docutils literal notranslate">collections.abc.Collection</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.Container">
class typing.Container(Generic[T_co])<a class="headerlink" href="#typing.Container" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="collections.abc.html#collections.abc.Container" title="collections.abc.Container"><code class="xref py py-class docutils literal notranslate">collections.abc.Container</code></a>.
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="collections.abc.html#collections.abc.Container" title="collections.abc.Container"><code class="xref py py-class docutils literal notranslate">collections.abc.Container</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.ItemsView">
class typing.ItemsView(MappingView, AbstractSet[tuple[KT_co, VT_co]])<a class="headerlink" href="#typing.ItemsView" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="collections.abc.html#collections.abc.ItemsView" title="collections.abc.ItemsView"><code class="xref py py-class docutils literal notranslate">collections.abc.ItemsView</code></a>.
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="collections.abc.html#collections.abc.ItemsView" title="collections.abc.ItemsView"><code class="xref py py-class docutils literal notranslate">collections.abc.ItemsView</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.KeysView">
class typing.KeysView(MappingView, AbstractSet[KT_co])<a class="headerlink" href="#typing.KeysView" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="collections.abc.html#collections.abc.KeysView" title="collections.abc.KeysView"><code class="xref py py-class docutils literal notranslate">collections.abc.KeysView</code></a>.
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="collections.abc.html#collections.abc.KeysView" title="collections.abc.KeysView"><code class="xref py py-class docutils literal notranslate">collections.abc.KeysView</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.Mapping">
class typing.Mapping(Collection[KT], Generic[KT, VT_co])<a class="headerlink" href="#typing.Mapping" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="collections.abc.html#collections.abc.Mapping" title="collections.abc.Mapping"><code class="xref py py-class docutils literal notranslate">collections.abc.Mapping</code></a>.
This type can be used as follows:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>def get_position_in_index(word_list: Mapping[str, int], word: str) -&gt; int:
 return word_list[word]
</pre></div>
</div>
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="collections.abc.html#collections.abc.Mapping" title="collections.abc.Mapping"><code class="xref py py-class docutils literal notranslate">collections.abc.Mapping</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.MappingView">
class typing.MappingView(Sized)<a class="headerlink" href="#typing.MappingView" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="collections.abc.html#collections.abc.MappingView" title="collections.abc.MappingView"><code class="xref py py-class docutils literal notranslate">collections.abc.MappingView</code></a>.
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="collections.abc.html#collections.abc.MappingView" title="collections.abc.MappingView"><code class="xref py py-class docutils literal notranslate">collections.abc.MappingView</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.MutableMapping">
class typing.MutableMapping(Mapping[KT, VT])<a class="headerlink" href="#typing.MutableMapping" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="collections.abc.html#collections.abc.MutableMapping" title="collections.abc.MutableMapping"><code class="xref py py-class docutils literal notranslate">collections.abc.MutableMapping</code></a>.
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="collections.abc.html#collections.abc.MutableMapping" title="collections.abc.MutableMapping"><code class="xref py py-class docutils literal notranslate">collections.abc.MutableMapping</code></a>
now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.MutableSequence">
class typing.MutableSequence(Sequence[T])<a class="headerlink" href="#typing.MutableSequence" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="collections.abc.html#collections.abc.MutableSequence" title="collections.abc.MutableSequence"><code class="xref py py-class docutils literal notranslate">collections.abc.MutableSequence</code></a>.
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="collections.abc.html#collections.abc.MutableSequence" title="collections.abc.MutableSequence"><code class="xref py py-class docutils literal notranslate">collections.abc.MutableSequence</code></a>
now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.MutableSet">
class typing.MutableSet(AbstractSet[T])<a class="headerlink" href="#typing.MutableSet" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="collections.abc.html#collections.abc.MutableSet" title="collections.abc.MutableSet"><code class="xref py py-class docutils literal notranslate">collections.abc.MutableSet</code></a>.
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="collections.abc.html#collections.abc.MutableSet" title="collections.abc.MutableSet"><code class="xref py py-class docutils literal notranslate">collections.abc.MutableSet</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.Sequence">
class typing.Sequence(Reversible[T_co], Collection[T_co])<a class="headerlink" href="#typing.Sequence" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="collections.abc.html#collections.abc.Sequence" title="collections.abc.Sequence"><code class="xref py py-class docutils literal notranslate">collections.abc.Sequence</code></a>.
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="collections.abc.html#collections.abc.Sequence" title="collections.abc.Sequence"><code class="xref py py-class docutils literal notranslate">collections.abc.Sequence</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.ValuesView">
class typing.ValuesView(MappingView, Collection[_VT_co])<a class="headerlink" href="#typing.ValuesView" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="collections.abc.html#collections.abc.ValuesView" title="collections.abc.ValuesView"><code class="xref py py-class docutils literal notranslate">collections.abc.ValuesView</code></a>.
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="collections.abc.html#collections.abc.ValuesView" title="collections.abc.ValuesView"><code class="xref py py-class docutils literal notranslate">collections.abc.ValuesView</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

</section>
<section id="corresponding-to-other-types-in-collections-abc">
<h4>Corresponding to other types in <a class="reference internal" href="collections.abc.html#module-collections.abc" title="collections.abc: Abstract base classes for containers"><code class="xref py py-mod docutils literal notranslate">collections.abc</code></a><a class="headerlink" href="#corresponding-to-other-types-in-collections-abc" title="Permalink to this headline">¶</a></h4>
<dl class="py class">
<dt class="sig sig-object py" id="typing.Iterable">
class typing.Iterable(Generic[T_co])<a class="headerlink" href="#typing.Iterable" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="collections.abc.html#collections.abc.Iterable" title="collections.abc.Iterable"><code class="xref py py-class docutils literal notranslate">collections.abc.Iterable</code></a>.
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="collections.abc.html#collections.abc.Iterable" title="collections.abc.Iterable"><code class="xref py py-class docutils literal notranslate">collections.abc.Iterable</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.Iterator">
class typing.Iterator(Iterable[T_co])<a class="headerlink" href="#typing.Iterator" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="collections.abc.html#collections.abc.Iterator" title="collections.abc.Iterator"><code class="xref py py-class docutils literal notranslate">collections.abc.Iterator</code></a>.
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="collections.abc.html#collections.abc.Iterator" title="collections.abc.Iterator"><code class="xref py py-class docutils literal notranslate">collections.abc.Iterator</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.Generator">
class typing.Generator(Iterator[T_co], Generic[T_co, T_contra, V_co])<a class="headerlink" href="#typing.Generator" title="Permalink to this definition">¶</a></dt>
<dd>A generator can be annotated by the generic type
<code class="docutils literal notranslate">Generator[YieldType, SendType, ReturnType]</code>. For example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>def echo_round() -&gt; Generator[int, float, str]:
 sent = yield 0
 while sent &gt;= 0:
 sent = yield round(sent)
 return &#39;Done&#39;
</pre></div>
</div>
Note that unlike many other generics in the typing module, the <code class="docutils literal notranslate">SendType</code>
of <a class="reference internal" href="#typing.Generator" title="typing.Generator"><code class="xref py py-class docutils literal notranslate">Generator</code></a> behaves contravariantly, not covariantly or
invariantly.
If your generator will only yield values, set the <code class="docutils literal notranslate">SendType</code> and
<code class="docutils literal notranslate">ReturnType</code> to <code class="docutils literal notranslate">None</code>:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>def infinite_stream(start: int) -&gt; Generator[int, None, None]:
 while True:
 yield start
 start += 1
</pre></div>
</div>
Alternatively, annotate your generator as having a return type of
either <code class="docutils literal notranslate">Iterable[YieldType]</code> or <code class="docutils literal notranslate">Iterator[YieldType]</code>:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>def infinite_stream(start: int) -&gt; Iterator[int]:
 while True:
 yield start
 start += 1
</pre></div>
</div>
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="collections.abc.html#collections.abc.Generator" title="collections.abc.Generator"><code class="xref py py-class docutils literal notranslate">collections.abc.Generator</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.Hashable">
class typing.Hashable<a class="headerlink" href="#typing.Hashable" title="Permalink to this definition">¶</a></dt>
<dd>An alias to <a class="reference internal" href="collections.abc.html#collections.abc.Hashable" title="collections.abc.Hashable"><code class="xref py py-class docutils literal notranslate">collections.abc.Hashable</code></a>.
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.Reversible">
class typing.Reversible(Iterable[T_co])<a class="headerlink" href="#typing.Reversible" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="collections.abc.html#collections.abc.Reversible" title="collections.abc.Reversible"><code class="xref py py-class docutils literal notranslate">collections.abc.Reversible</code></a>.
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="collections.abc.html#collections.abc.Reversible" title="collections.abc.Reversible"><code class="xref py py-class docutils literal notranslate">collections.abc.Reversible</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.Sized">
class typing.Sized<a class="headerlink" href="#typing.Sized" title="Permalink to this definition">¶</a></dt>
<dd>An alias to <a class="reference internal" href="collections.abc.html#collections.abc.Sized" title="collections.abc.Sized"><code class="xref py py-class docutils literal notranslate">collections.abc.Sized</code></a>.
</dd></dl>

</section>
<section id="asynchronous-programming">
<h4>Asynchronous programming<a class="headerlink" href="#asynchronous-programming" title="Permalink to this headline">¶</a></h4>
<dl class="py class">
<dt class="sig sig-object py" id="typing.Coroutine">
class typing.Coroutine(Awaitable[V_co], Generic[T_co, T_contra, V_co])<a class="headerlink" href="#typing.Coroutine" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="collections.abc.html#collections.abc.Coroutine" title="collections.abc.Coroutine"><code class="xref py py-class docutils literal notranslate">collections.abc.Coroutine</code></a>.
The variance and order of type variables
correspond to those of <a class="reference internal" href="#typing.Generator" title="typing.Generator"><code class="xref py py-class docutils literal notranslate">Generator</code></a>, for example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>from collections.abc import Coroutine
c: Coroutine[list[str], str, int] # Some coroutine defined elsewhere
x = c.send(&#39;hi&#39;) # Inferred type of &#39;x&#39; is list[str]
async def bar() -&gt; None:
 y = await c # Inferred type of &#39;y&#39; is int
</pre></div>
</div>
<div class="versionadded">
New in version 3.5.3.
</div>
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="collections.abc.html#collections.abc.Coroutine" title="collections.abc.Coroutine"><code class="xref py py-class docutils literal notranslate">collections.abc.Coroutine</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.AsyncGenerator">
class typing.AsyncGenerator(AsyncIterator[T_co], Generic[T_co, T_contra])<a class="headerlink" href="#typing.AsyncGenerator" title="Permalink to this definition">¶</a></dt>
<dd>An async generator can be annotated by the generic type
<code class="docutils literal notranslate">AsyncGenerator[YieldType, SendType]</code>. For example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>async def echo_round() -&gt; AsyncGenerator[int, float]:
 sent = yield 0
 while sent &gt;= 0.0:
 rounded = await round(sent)
 sent = yield rounded
</pre></div>
</div>
Unlike normal generators, async generators cannot return a value, so there
is no <code class="docutils literal notranslate">ReturnType</code> type parameter. As with <a class="reference internal" href="#typing.Generator" title="typing.Generator"><code class="xref py py-class docutils literal notranslate">Generator</code></a>, the
<code class="docutils literal notranslate">SendType</code> behaves contravariantly.
If your generator will only yield values, set the <code class="docutils literal notranslate">SendType</code> to
<code class="docutils literal notranslate">None</code>:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>async def infinite_stream(start: int) -&gt; AsyncGenerator[int, None]:
 while True:
 yield start
 start = await increment(start)
</pre></div>
</div>
Alternatively, annotate your generator as having a return type of
either <code class="docutils literal notranslate">AsyncIterable[YieldType]</code> or <code class="docutils literal notranslate">AsyncIterator[YieldType]</code>:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>async def infinite_stream(start: int) -&gt; AsyncIterator[int]:
 while True:
 yield start
 start = await increment(start)
</pre></div>
</div>
<div class="versionadded">
New in version 3.6.1.
</div>
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="collections.abc.html#collections.abc.AsyncGenerator" title="collections.abc.AsyncGenerator"><code class="xref py py-class docutils literal notranslate">collections.abc.AsyncGenerator</code></a>
now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.AsyncIterable">
class typing.AsyncIterable(Generic[T_co])<a class="headerlink" href="#typing.AsyncIterable" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="collections.abc.html#collections.abc.AsyncIterable" title="collections.abc.AsyncIterable"><code class="xref py py-class docutils literal notranslate">collections.abc.AsyncIterable</code></a>.
<div class="versionadded">
New in version 3.5.2.
</div>
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="collections.abc.html#collections.abc.AsyncIterable" title="collections.abc.AsyncIterable"><code class="xref py py-class docutils literal notranslate">collections.abc.AsyncIterable</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.AsyncIterator">
class typing.AsyncIterator(AsyncIterable[T_co])<a class="headerlink" href="#typing.AsyncIterator" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="collections.abc.html#collections.abc.AsyncIterator" title="collections.abc.AsyncIterator"><code class="xref py py-class docutils literal notranslate">collections.abc.AsyncIterator</code></a>.
<div class="versionadded">
New in version 3.5.2.
</div>
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="collections.abc.html#collections.abc.AsyncIterator" title="collections.abc.AsyncIterator"><code class="xref py py-class docutils literal notranslate">collections.abc.AsyncIterator</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.Awaitable">
class typing.Awaitable(Generic[T_co])<a class="headerlink" href="#typing.Awaitable" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="collections.abc.html#collections.abc.Awaitable" title="collections.abc.Awaitable"><code class="xref py py-class docutils literal notranslate">collections.abc.Awaitable</code></a>.
<div class="versionadded">
New in version 3.5.2.
</div>
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="collections.abc.html#collections.abc.Awaitable" title="collections.abc.Awaitable"><code class="xref py py-class docutils literal notranslate">collections.abc.Awaitable</code></a> now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

</section>
<section id="context-manager-types">
<h4>Context manager types<a class="headerlink" href="#context-manager-types" title="Permalink to this headline">¶</a></h4>
<dl class="py class">
<dt class="sig sig-object py" id="typing.ContextManager">
class typing.ContextManager(Generic[T_co])<a class="headerlink" href="#typing.ContextManager" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="contextlib.html#contextlib.AbstractContextManager" title="contextlib.AbstractContextManager"><code class="xref py py-class docutils literal notranslate">contextlib.AbstractContextManager</code></a>.
<div class="versionadded">
New in version 3.5.4.
</div>
<div class="versionadded">
New in version 3.6.0.
</div>
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="contextlib.html#contextlib.AbstractContextManager" title="contextlib.AbstractContextManager"><code class="xref py py-class docutils literal notranslate">contextlib.AbstractContextManager</code></a>
now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.AsyncContextManager">
class typing.AsyncContextManager(Generic[T_co])<a class="headerlink" href="#typing.AsyncContextManager" title="Permalink to this definition">¶</a></dt>
<dd>A generic version of <a class="reference internal" href="contextlib.html#contextlib.AbstractAsyncContextManager" title="contextlib.AbstractAsyncContextManager"><code class="xref py py-class docutils literal notranslate">contextlib.AbstractAsyncContextManager</code></a>.
<div class="versionadded">
New in version 3.5.4.
</div>
<div class="versionadded">
New in version 3.6.2.
</div>
<div class="deprecated">
Deprecated since version 3.9: <a class="reference internal" href="contextlib.html#contextlib.AbstractAsyncContextManager" title="contextlib.AbstractAsyncContextManager"><code class="xref py py-class docutils literal notranslate">contextlib.AbstractAsyncContextManager</code></a>
now supports subscripting (<code class="docutils literal notranslate">[]</code>).
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> and <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a>.
</div>
</dd></dl>

</section>
</section>
<section id="protocols">
<h3>Protocols<a class="headerlink" href="#protocols" title="Permalink to this headline">¶</a></h3>
These protocols are decorated with <a class="reference internal" href="#typing.runtime_checkable" title="typing.runtime_checkable"><code class="xref py py-func docutils literal notranslate">runtime_checkable()</code></a>.
<dl class="py class">
<dt class="sig sig-object py" id="typing.SupportsAbs">
class typing.SupportsAbs<a class="headerlink" href="#typing.SupportsAbs" title="Permalink to this definition">¶</a></dt>
<dd>An ABC with one abstract method <code class="docutils literal notranslate">__abs__</code> that is covariant
in its return type.
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.SupportsBytes">
class typing.SupportsBytes<a class="headerlink" href="#typing.SupportsBytes" title="Permalink to this definition">¶</a></dt>
<dd>An ABC with one abstract method <code class="docutils literal notranslate">__bytes__</code>.
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.SupportsComplex">
class typing.SupportsComplex<a class="headerlink" href="#typing.SupportsComplex" title="Permalink to this definition">¶</a></dt>
<dd>An ABC with one abstract method <code class="docutils literal notranslate">__complex__</code>.
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.SupportsFloat">
class typing.SupportsFloat<a class="headerlink" href="#typing.SupportsFloat" title="Permalink to this definition">¶</a></dt>
<dd>An ABC with one abstract method <code class="docutils literal notranslate">__float__</code>.
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.SupportsIndex">
class typing.SupportsIndex<a class="headerlink" href="#typing.SupportsIndex" title="Permalink to this definition">¶</a></dt>
<dd>An ABC with one abstract method <code class="docutils literal notranslate">__index__</code>.
<div class="versionadded">
New in version 3.8.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.SupportsInt">
class typing.SupportsInt<a class="headerlink" href="#typing.SupportsInt" title="Permalink to this definition">¶</a></dt>
<dd>An ABC with one abstract method <code class="docutils literal notranslate">__int__</code>.
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.SupportsRound">
class typing.SupportsRound<a class="headerlink" href="#typing.SupportsRound" title="Permalink to this definition">¶</a></dt>
<dd>An ABC with one abstract method <code class="docutils literal notranslate">__round__</code>
that is covariant in its return type.
</dd></dl>

</section>
<section id="functions-and-decorators">
<h3>Functions and decorators<a class="headerlink" href="#functions-and-decorators" title="Permalink to this headline">¶</a></h3>
<dl class="py function">
<dt class="sig sig-object py" id="typing.cast">
typing.cast(typ, val)<a class="headerlink" href="#typing.cast" title="Permalink to this definition">¶</a></dt>
<dd>Cast a value to a type.
This returns the value unchanged. To the type checker this
signals that the return value has the designated type, but at
runtime we intentionally don’t check anything (we want this
to be as fast as possible).
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="typing.overload">
&#64;typing.overload<a class="headerlink" href="#typing.overload" title="Permalink to this definition">¶</a></dt>
<dd>The <code class="docutils literal notranslate">&#64;overload</code> decorator allows describing functions and methods
that support multiple different combinations of argument types. A series
of <code class="docutils literal notranslate">&#64;overload</code>-decorated definitions must be followed by exactly one
non-<code class="docutils literal notranslate">&#64;overload</code>-decorated definition (for the same function/method).
The <code class="docutils literal notranslate">&#64;overload</code>-decorated definitions are for the benefit of the
type checker only, since they will be overwritten by the
non-<code class="docutils literal notranslate">&#64;overload</code>-decorated definition, while the latter is used at
runtime but should be ignored by a type checker. At runtime, calling
a <code class="docutils literal notranslate">&#64;overload</code>-decorated function directly will raise
<a class="reference internal" href="exceptions.html#NotImplementedError" title="NotImplementedError"><code class="xref py py-exc docutils literal notranslate">NotImplementedError</code></a>. An example of overload that gives a more
precise type than can be expressed using a union or a type variable:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>@overload
def process(response: None) -&gt; None:
 ...
@overload
def process(response: int) -&gt; tuple[int, str]:
 ...
@overload
def process(response: bytes) -&gt; str:
 ...
def process(response):
 &lt;actual implementation&gt;
</pre></div>
</div>
See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0484">PEP 484</a> for more details and comparison with other typing semantics.
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="typing.final">
&#64;typing.final<a class="headerlink" href="#typing.final" title="Permalink to this definition">¶</a></dt>
<dd>A decorator to indicate to type checkers that the decorated method
cannot be overridden, and the decorated class cannot be subclassed.
For example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>class Base:
 @final
 def done(self) -&gt; None:
 ...
class Sub(Base):
 def done(self) -&gt; None: # Error reported by type checker
 ...

@final
class Leaf:
 ...
class Other(Leaf): # Error reported by type checker
 ...
</pre></div>
</div>
There is no runtime checking of these properties. See <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0591">PEP 591</a> for
more details.
<div class="versionadded">
New in version 3.8.
</div>
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="typing.no_type_check">
&#64;typing.no_type_check<a class="headerlink" href="#typing.no_type_check" title="Permalink to this definition">¶</a></dt>
<dd>Decorator to indicate that annotations are not type hints.
This works as class or function <a class="reference internal" href="../glossary.html#term-decorator">decorator</a>. With a class, it
applies recursively to all methods defined in that class (but not
to methods defined in its superclasses or subclasses).
This mutates the function(s) in place.
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="typing.no_type_check_decorator">
&#64;typing.no_type_check_decorator<a class="headerlink" href="#typing.no_type_check_decorator" title="Permalink to this definition">¶</a></dt>
<dd>Decorator to give another decorator the <a class="reference internal" href="#typing.no_type_check" title="typing.no_type_check"><code class="xref py py-func docutils literal notranslate">no_type_check()</code></a> effect.
This wraps the decorator with something that wraps the decorated
function in <a class="reference internal" href="#typing.no_type_check" title="typing.no_type_check"><code class="xref py py-func docutils literal notranslate">no_type_check()</code></a>.
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="typing.type_check_only">
&#64;typing.type_check_only<a class="headerlink" href="#typing.type_check_only" title="Permalink to this definition">¶</a></dt>
<dd>Decorator to mark a class or function to be unavailable at runtime.
This decorator is itself not available at runtime. It is mainly
intended to mark classes that are defined in type stub files if
an implementation returns an instance of a private class:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>@type_check_only
class Response: # private or not available at runtime
 code: int
 def get_header(self, name: str) -&gt; str: ...

def fetch_response() -&gt; Response: ...
</pre></div>
</div>
Note that returning instances of private classes is not recommended.
It is usually preferable to make such classes public.
</dd></dl>

</section>
<section id="introspection-helpers">
<h3>Introspection helpers<a class="headerlink" href="#introspection-helpers" title="Permalink to this headline">¶</a></h3>
<dl class="py function">
<dt class="sig sig-object py" id="typing.get_type_hints">
typing.get_type_hints(obj, globalns=None, localns=None, include_extras=False)<a class="headerlink" href="#typing.get_type_hints" title="Permalink to this definition">¶</a></dt>
<dd>Return a dictionary containing type hints for a function, method, module
or class object.
This is often the same as <code class="docutils literal notranslate">obj.__annotations__</code>. In addition,
forward references encoded as string literals are handled by evaluating
them in <code class="docutils literal notranslate">globals</code> and <code class="docutils literal notranslate">locals</code> namespaces. If necessary,
<code class="docutils literal notranslate">Optional[t]</code> is added for function and method annotations if a default
value equal to <code class="docutils literal notranslate">None</code> is set. For a class <code class="docutils literal notranslate">C</code>, return
a dictionary constructed by merging all the <code class="docutils literal notranslate">__annotations__</code> along
<code class="docutils literal notranslate">C.__mro__</code> in reverse order.
The function recursively replaces all <code class="docutils literal notranslate">Annotated[T, ...]</code> with <code class="docutils literal notranslate">T</code>,
unless <code class="docutils literal notranslate">include_extras</code> is set to <code class="docutils literal notranslate">True</code> (see <a class="reference internal" href="#typing.Annotated" title="typing.Annotated"><code class="xref py py-class docutils literal notranslate">Annotated</code></a> for
more information). For example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>class Student(NamedTuple):
 name: Annotated[str, &#39;some marker&#39;]

get_type_hints(Student) == {&#39;name&#39;: str}
get_type_hints(Student, include_extras=False) == {&#39;name&#39;: str}
get_type_hints(Student, include_extras=True) == {
 &#39;name&#39;: Annotated[str, &#39;some marker&#39;]
}
</pre></div>
</div>
<div class="admonition note">
Note
<a class="reference internal" href="#typing.get_type_hints" title="typing.get_type_hints"><code class="xref py py-func docutils literal notranslate">get_type_hints()</code></a> does not work with imported
<a class="reference internal" href="#type-aliases">type aliases</a> that include forward references.
Enabling postponed evaluation of annotations (<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0563">PEP 563</a>) may remove
the need for most forward references.
</div>
<div class="versionchanged">
Changed in version 3.9: Added <code class="docutils literal notranslate">include_extras</code> parameter as part of <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0593">PEP 593</a>.
</div>
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="typing.get_args">
typing.get_args(tp)<a class="headerlink" href="#typing.get_args" title="Permalink to this definition">¶</a></dt>
<dd></dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="typing.get_origin">
typing.get_origin(tp)<a class="headerlink" href="#typing.get_origin" title="Permalink to this definition">¶</a></dt>
<dd>Provide basic introspection for generic types and special typing forms.
For a typing object of the form <code class="docutils literal notranslate">X[Y, Z, ...]</code> these functions return
<code class="docutils literal notranslate">X</code> and <code class="docutils literal notranslate">(Y, Z, ...)</code>. If <code class="docutils literal notranslate">X</code> is a generic alias for a builtin or
<a class="reference internal" href="collections.html#module-collections" title="collections: Container datatypes"><code class="xref py py-mod docutils literal notranslate">collections</code></a> class, it gets normalized to the original class.
If <code class="docutils literal notranslate">X</code> is a union or <a class="reference internal" href="#typing.Literal" title="typing.Literal"><code class="xref py py-class docutils literal notranslate">Literal</code></a> contained in another
generic type, the order of <code class="docutils literal notranslate">(Y, Z, ...)</code> may be different from the order
of the original arguments <code class="docutils literal notranslate">[Y, Z, ...]</code> due to type caching.
For unsupported objects return <code class="docutils literal notranslate">None</code> and <code class="docutils literal notranslate">()</code> correspondingly.
Examples:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>assert get_origin(Dict[str, int]) is dict
assert get_args(Dict[int, str]) == (int, str)

assert get_origin(Union[int, str]) is Union
assert get_args(Union[int, str]) == (int, str)
</pre></div>
</div>
<div class="versionadded">
New in version 3.8.
</div>
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="typing.is_typeddict">
typing.is_typeddict(tp)<a class="headerlink" href="#typing.is_typeddict" title="Permalink to this definition">¶</a></dt>
<dd>Check if a type is a <a class="reference internal" href="#typing.TypedDict" title="typing.TypedDict"><code class="xref py py-class docutils literal notranslate">TypedDict</code></a>.
For example:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>class Film(TypedDict):
 title: str
 year: int

is_typeddict(Film) # =&gt; True
is_typeddict(list | str) # =&gt; False
</pre></div>
</div>
<div class="versionadded">
New in version 3.10.
</div>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="typing.ForwardRef">
class typing.ForwardRef<a class="headerlink" href="#typing.ForwardRef" title="Permalink to this definition">¶</a></dt>
<dd>A class used for internal typing representation of string forward references.
For example, <code class="docutils literal notranslate">List[&quot;SomeClass&quot;]</code> is implicitly transformed into
<code class="docutils literal notranslate">List[ForwardRef(&quot;SomeClass&quot;)]</code>. This class should not be instantiated by
a user, but may be used by introspection tools.
<div class="admonition note">
Note
<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0585">PEP 585</a> generic types such as <code class="docutils literal notranslate">list[&quot;SomeClass&quot;]</code> will not be
implicitly transformed into <code class="docutils literal notranslate">list[ForwardRef(&quot;SomeClass&quot;)]</code> and thus
will not automatically resolve to <code class="docutils literal notranslate">list[SomeClass]</code>.
</div>
<div class="versionadded">
New in version 3.7.4.
</div>
</dd></dl>

</section>
<section id="constant">
<h3>Constant<a class="headerlink" href="#constant" title="Permalink to this headline">¶</a></h3>
<dl class="py data">
<dt class="sig sig-object py" id="typing.TYPE_CHECKING">
typing.TYPE_CHECKING<a class="headerlink" href="#typing.TYPE_CHECKING" title="Permalink to this definition">¶</a></dt>
<dd>A special constant that is assumed to be <code class="docutils literal notranslate">True</code> by 3rd party static
type checkers. It is <code class="docutils literal notranslate">False</code> at runtime. Usage:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>if TYPE_CHECKING:
 import expensive_mod

def fun(arg: &#39;expensive_mod.SomeType&#39;) -&gt; None:
 local_var: expensive_mod.AnotherType = other_fun()
</pre></div>
</div>
The first type annotation must be enclosed in quotes, making it a
“forward reference”, to hide the <code class="docutils literal notranslate">expensive_mod</code> reference from the
interpreter runtime. Type annotations for local variables are not
evaluated, so the second annotation does not need to be enclosed in quotes.
<div class="admonition note">
Note
If <code class="docutils literal notranslate">from __future__ import annotations</code> is used,
annotations are not evaluated at function definition time.
Instead, they are stored as strings in <code class="docutils literal notranslate">__annotations__</code>.
This makes it unnecessary to use quotes around the annotation
(see <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0563">PEP 563</a>).
</div>
<div class="versionadded">
New in version 3.5.2.
</div>
</dd></dl>

</section>
</section>
</section>

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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="#"><code class="xref py py-mod docutils literal notranslate">typing</code> — Support for type hints</a><ul>
<li><a class="reference internal" href="#relevant-peps">Relevant PEPs</a></li>
<li><a class="reference internal" href="#type-aliases">Type aliases</a></li>
<li><a class="reference internal" href="#newtype">NewType</a></li>
<li><a class="reference internal" href="#callable">Callable</a></li>
<li><a class="reference internal" href="#generics">Generics</a></li>
<li><a class="reference internal" href="#user-defined-generic-types">User-defined generic types</a></li>
<li><a class="reference internal" href="#the-any-type">The <code class="xref py py-data docutils literal notranslate">Any</code> type</a></li>
<li><a class="reference internal" href="#nominal-vs-structural-subtyping">Nominal vs structural subtyping</a></li>
<li><a class="reference internal" href="#module-contents">Module contents</a><ul>
<li><a class="reference internal" href="#special-typing-primitives">Special typing primitives</a><ul>
<li><a class="reference internal" href="#special-types">Special types</a></li>
<li><a class="reference internal" href="#special-forms">Special forms</a></li>
<li><a class="reference internal" href="#building-generic-types">Building generic types</a></li>
<li><a class="reference internal" href="#other-special-directives">Other special directives</a></li>
</ul>
</li>
<li><a class="reference internal" href="#generic-concrete-collections">Generic concrete collections</a><ul>
<li><a class="reference internal" href="#corresponding-to-built-in-types">Corresponding to built-in types</a></li>
<li><a class="reference internal" href="#corresponding-to-types-in-collections">Corresponding to types in <code class="xref py py-mod docutils literal notranslate">collections</code></a></li>
<li><a class="reference internal" href="#other-concrete-types">Other concrete types</a></li>
</ul>
</li>
<li><a class="reference internal" href="#abstract-base-classes">Abstract Base Classes</a><ul>
<li><a class="reference internal" href="#corresponding-to-collections-in-collections-abc">Corresponding to collections in <code class="xref py py-mod docutils literal notranslate">collections.abc</code></a></li>
<li><a class="reference internal" href="#corresponding-to-other-types-in-collections-abc">Corresponding to other types in <code class="xref py py-mod docutils literal notranslate">collections.abc</code></a></li>
<li><a class="reference internal" href="#asynchronous-programming">Asynchronous programming</a></li>
<li><a class="reference internal" href="#context-manager-types">Context manager types</a></li>
</ul>
</li>
<li><a class="reference internal" href="#protocols">Protocols</a></li>
<li><a class="reference internal" href="#functions-and-decorators">Functions and decorators</a></li>
<li><a class="reference internal" href="#introspection-helpers">Introspection helpers</a></li>
<li><a class="reference internal" href="#constant">Constant</a></li>
</ul>
</li>
</ul>
</li>
</ul>

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