Gecko [ fernandoquevedodop.com ]

Name	Size	Permission
2to3.html	70.96 KB	-rw-r--r--
__future__.html	20.75 KB	-rw-r--r--
__main__.html	44.87 KB	-rw-r--r--
_thread.html	30.39 KB	-rw-r--r--
abc.html	46.87 KB	-rw-r--r--
aifc.html	35.56 KB	-rw-r--r--
allos.html	34.33 KB	-rw-r--r--
archiving.html	17 KB	-rw-r--r--
argparse.html	300.89 KB	-rw-r--r--
array.html	37.28 KB	-rw-r--r--
ast.html	293.08 KB	-rw-r--r--
asynchat.html	37.41 KB	-rw-r--r--
asyncio-api-index.html	27.68 KB	-rw-r--r--
asyncio-dev.html	36.1 KB	-rw-r--r--
asyncio-eventloop.html	204.43 KB	-rw-r--r--
asyncio-exceptions.html	17.11 KB	-rw-r--r--
asyncio-future.html	38.23 KB	-rw-r--r--
asyncio-llapi-index.html	61.97 KB	-rw-r--r--
asyncio-platforms.html	21.77 KB	-rw-r--r--
asyncio-policy.html	39.56 KB	-rw-r--r--
asyncio-protocol.html	118.33 KB	-rw-r--r--
asyncio-queue.html	31.86 KB	-rw-r--r--
asyncio-stream.html	69.98 KB	-rw-r--r--
asyncio-subprocess.html	49.25 KB	-rw-r--r--
asyncio-sync.html	42.79 KB	-rw-r--r--
asyncio-task.html	109.14 KB	-rw-r--r--
asyncio.html	17.31 KB	-rw-r--r--
asyncore.html	49.36 KB	-rw-r--r--
atexit.html	22.87 KB	-rw-r--r--
audioop.html	46 KB	-rw-r--r--
audit_events.html	72.85 KB	-rw-r--r--
base64.html	48.09 KB	-rw-r--r--
bdb.html	66 KB	-rw-r--r--
binary.html	15.97 KB	-rw-r--r--
binascii.html	36.3 KB	-rw-r--r--
binhex.html	15.97 KB	-rw-r--r--
bisect.html	43.38 KB	-rw-r--r--
builtins.html	14.87 KB	-rw-r--r--
bz2.html	50.68 KB	-rw-r--r--
calendar.html	69.35 KB	-rw-r--r--
cgi.html	59.95 KB	-rw-r--r--
cgitb.html	19.96 KB	-rw-r--r--
chunk.html	22.21 KB	-rw-r--r--
cmath.html	43.89 KB	-rw-r--r--
cmd.html	50.42 KB	-rw-r--r--
code.html	35.38 KB	-rw-r--r--
codecs.html	157.96 KB	-rw-r--r--
codeop.html	18.26 KB	-rw-r--r--
collections.abc.html	79.17 KB	-rw-r--r--
collections.html	189.43 KB	-rw-r--r--
colorsys.html	17.31 KB	-rw-r--r--
compileall.html	50.68 KB	-rw-r--r--
concurrency.html	24.15 KB	-rw-r--r--
concurrent.futures.html	79.03 KB	-rw-r--r--
concurrent.html	11.56 KB	-rw-r--r--
configparser.html	159.4 KB	-rw-r--r--
constants.html	22.41 KB	-rw-r--r--
contextlib.html	117.2 KB	-rw-r--r--
contextvars.html	38.38 KB	-rw-r--r--
copy.html	17.92 KB	-rw-r--r--
copyreg.html	18.63 KB	-rw-r--r--
crypt.html	28.29 KB	-rw-r--r--
crypto.html	13.93 KB	-rw-r--r--
csv.html	82.89 KB	-rw-r--r--
ctypes.html	295.49 KB	-rw-r--r--
curses.ascii.html	32.04 KB	-rw-r--r--
curses.html	221.24 KB	-rw-r--r--
curses.panel.html	22.16 KB	-rw-r--r--
custominterp.html	11.85 KB	-rw-r--r--
dataclasses.html	113.16 KB	-rw-r--r--
datatypes.html	31.82 KB	-rw-r--r--
datetime.html	374.92 KB	-rw-r--r--
dbm.html	51.16 KB	-rw-r--r--
debug.html	17 KB	-rw-r--r--
decimal.html	270.12 KB	-rw-r--r--
development.html	32.34 KB	-rw-r--r--
devmode.html	31.72 KB	-rw-r--r--
dialog.html	43.03 KB	-rw-r--r--
difflib.html	111.99 KB	-rw-r--r--
dis.html	136.07 KB	-rw-r--r--
distribution.html	13.67 KB	-rw-r--r--
distutils.html	14.73 KB	-rw-r--r--
doctest.html	199.32 KB	-rw-r--r--
email.charset.html	31.92 KB	-rw-r--r--
email.compat32-message.html	97.74 KB	-rw-r--r--
email.contentmanager.html	37.02 KB	-rw-r--r--
email.encoders.html	18.47 KB	-rw-r--r--
email.errors.html	24.45 KB	-rw-r--r--
email.examples.html	60.49 KB	-rw-r--r--
email.generator.html	48.79 KB	-rw-r--r--
email.header.html	37.61 KB	-rw-r--r--
email.headerregistry.html	66.26 KB	-rw-r--r--
email.html	30.75 KB	-rw-r--r--
email.iterators.html	18.23 KB	-rw-r--r--
email.message.html	99.75 KB	-rw-r--r--
email.mime.html	44.89 KB	-rw-r--r--
email.parser.html	57.39 KB	-rw-r--r--
email.policy.html	84.24 KB	-rw-r--r--
email.utils.html	42.57 KB	-rw-r--r--
ensurepip.html	23.9 KB	-rw-r--r--
enum.html	151 KB	-rw-r--r--
errno.html	60.17 KB	-rw-r--r--
exceptions.html	108.44 KB	-rw-r--r--
faulthandler.html	31.5 KB	-rw-r--r--
fcntl.html	36.67 KB	-rw-r--r--
filecmp.html	32.08 KB	-rw-r--r--
fileformats.html	13.52 KB	-rw-r--r--
fileinput.html	40.37 KB	-rw-r--r--
filesys.html	16.78 KB	-rw-r--r--
fnmatch.html	21.02 KB	-rw-r--r--
fractions.html	35.29 KB	-rw-r--r--
frameworks.html	16.15 KB	-rw-r--r--
ftplib.html	71.97 KB	-rw-r--r--
functional.html	12.19 KB	-rw-r--r--
functions.html	260.33 KB	-rw-r--r--
functools.html	92.96 KB	-rw-r--r--
gc.html	40.97 KB	-rw-r--r--
getopt.html	29.4 KB	-rw-r--r--
getpass.html	16.01 KB	-rw-r--r--
gettext.html	98.02 KB	-rw-r--r--
glob.html	27.2 KB	-rw-r--r--
graphlib.html	34.82 KB	-rw-r--r--
grp.html	16.03 KB	-rw-r--r--
gzip.html	45.65 KB	-rw-r--r--
hashlib.html	93.19 KB	-rw-r--r--
heapq.html	42.43 KB	-rw-r--r--
hmac.html	24.74 KB	-rw-r--r--
html.entities.html	14.91 KB	-rw-r--r--
html.html	14.81 KB	-rw-r--r--
html.parser.html	47.7 KB	-rw-r--r--
http.client.html	85.63 KB	-rw-r--r--
http.cookiejar.html	113.94 KB	-rw-r--r--
http.cookies.html	47.64 KB	-rw-r--r--
http.html	45.52 KB	-rw-r--r--
http.server.html	73.05 KB	-rw-r--r--
i18n.html	13.44 KB	-rw-r--r--
idle.html	77.18 KB	-rw-r--r--
imaplib.html	87.08 KB	-rw-r--r--
imghdr.html	17.94 KB	-rw-r--r--
imp.html	54.32 KB	-rw-r--r--
importlib.html	239.96 KB	-rw-r--r--
importlib.metadata.html	43.14 KB	-rw-r--r--
index.html	75.06 KB	-rw-r--r--
inspect.html	168.74 KB	-rw-r--r--
internet.html	29.89 KB	-rw-r--r--
intro.html	13.81 KB	-rw-r--r--
io.html	154.15 KB	-rw-r--r--
ipaddress.html	137.75 KB	-rw-r--r--
ipc.html	12.6 KB	-rw-r--r--
itertools.html	153.27 KB	-rw-r--r--
json.html	98.9 KB	-rw-r--r--
keyword.html	14.88 KB	-rw-r--r--
language.html	16.71 KB	-rw-r--r--
linecache.html	18.09 KB	-rw-r--r--
locale.html	77.35 KB	-rw-r--r--
logging.config.html	100.3 KB	-rw-r--r--
logging.handlers.html	146.28 KB	-rw-r--r--
logging.html	169.67 KB	-rw-r--r--
lzma.html	66.89 KB	-rw-r--r--
mailbox.html	176.34 KB	-rw-r--r--
mailcap.html	20.86 KB	-rw-r--r--
markup.html	22.31 KB	-rw-r--r--
marshal.html	24.43 KB	-rw-r--r--
math.html	85.82 KB	-rw-r--r--
mimetypes.html	40.27 KB	-rw-r--r--
mm.html	11.16 KB	-rw-r--r--
mmap.html	55.53 KB	-rw-r--r--
modulefinder.html	23.67 KB	-rw-r--r--
modules.html	15.88 KB	-rw-r--r--
msilib.html	78.38 KB	-rw-r--r--
msvcrt.html	29.22 KB	-rw-r--r--
multiprocessing.html	405.24 KB	-rw-r--r--
multiprocessing.shared_memory....	60 KB	-rw-r--r--
netdata.html	20.24 KB	-rw-r--r--
netrc.html	20.39 KB	-rw-r--r--
nis.html	16.76 KB	-rw-r--r--
nntplib.html	84.93 KB	-rw-r--r--
numbers.html	45.67 KB	-rw-r--r--
numeric.html	19.29 KB	-rw-r--r--
operator.html	107.32 KB	-rw-r--r--
optparse.html	256.96 KB	-rw-r--r--
os.html	594.39 KB	-rw-r--r--
os.path.html	65.54 KB	-rw-r--r--
ossaudiodev.html	56.35 KB	-rw-r--r--
pathlib.html	170.01 KB	-rw-r--r--
pdb.html	68.67 KB	-rw-r--r--
persistence.html	19.13 KB	-rw-r--r--
pickle.html	154.45 KB	-rw-r--r--
pickletools.html	22.92 KB	-rw-r--r--
pipes.html	21.7 KB	-rw-r--r--
pkgutil.html	42.76 KB	-rw-r--r--
platform.html	45.08 KB	-rw-r--r--
plistlib.html	30.06 KB	-rw-r--r--
poplib.html	41.42 KB	-rw-r--r--
posix.html	20.96 KB	-rw-r--r--
pprint.html	55.35 KB	-rw-r--r--
profile.html	84.63 KB	-rw-r--r--
pty.html	23.7 KB	-rw-r--r--
pwd.html	16.84 KB	-rw-r--r--
py_compile.html	29 KB	-rw-r--r--
pyclbr.html	24.06 KB	-rw-r--r--
pydoc.html	19.59 KB	-rw-r--r--
pyexpat.html	104.38 KB	-rw-r--r--
python.html	22.46 KB	-rw-r--r--
queue.html	43.39 KB	-rw-r--r--
quopri.html	18.64 KB	-rw-r--r--
random.html	86.31 KB	-rw-r--r--
re.html	214.24 KB	-rw-r--r--
readline.html	50.19 KB	-rw-r--r--
reprlib.html	30.85 KB	-rw-r--r--
resource.html	48.26 KB	-rw-r--r--
rlcompleter.html	18.06 KB	-rw-r--r--
runpy.html	30.99 KB	-rw-r--r--
sched.html	27.04 KB	-rw-r--r--
secrets.html	30.2 KB	-rw-r--r--
security_warnings.html	16.21 KB	-rw-r--r--
select.html	74.58 KB	-rw-r--r--
selectors.html	41.91 KB	-rw-r--r--
shelve.html	36.54 KB	-rw-r--r--
shlex.html	61.03 KB	-rw-r--r--
shutil.html	100.13 KB	-rw-r--r--
signal.html	95.39 KB	-rw-r--r--
site.html	38.16 KB	-rw-r--r--
smtpd.html	44.09 KB	-rw-r--r--
smtplib.html	81.4 KB	-rw-r--r--
sndhdr.html	16.4 KB	-rw-r--r--
socket.html	256.95 KB	-rw-r--r--
socketserver.html	91.95 KB	-rw-r--r--
spwd.html	16.71 KB	-rw-r--r--
sqlite3.html	225.51 KB	-rw-r--r--
ssl.html	328.83 KB	-rw-r--r--
stat.html	57.79 KB	-rw-r--r--
statistics.html	123.22 KB	-rw-r--r--
stdtypes.html	615.43 KB	-rw-r--r--
string.html	108.03 KB	-rw-r--r--
stringprep.html	24.94 KB	-rw-r--r--
struct.html	70.58 KB	-rw-r--r--
subprocess.html	199.03 KB	-rw-r--r--
sunau.html	39.84 KB	-rw-r--r--
superseded.html	26.21 KB	-rw-r--r--
symtable.html	33.26 KB	-rw-r--r--
sys.html	198.83 KB	-rw-r--r--
sysconfig.html	39.81 KB	-rw-r--r--
syslog.html	27.36 KB	-rw-r--r--
tabnanny.html	16.18 KB	-rw-r--r--
tarfile.html	161.92 KB	-rw-r--r--
telnetlib.html	38.21 KB	-rw-r--r--
tempfile.html	58.39 KB	-rw-r--r--
termios.html	22.86 KB	-rw-r--r--
test.html	222.85 KB	-rw-r--r--
text.html	16.8 KB	-rw-r--r--
textwrap.html	48.83 KB	-rw-r--r--
threading.html	128.33 KB	-rw-r--r--
time.html	107.46 KB	-rw-r--r--
timeit.html	52.63 KB	-rw-r--r--
tk.html	28.08 KB	-rw-r--r--
tkinter.colorchooser.html	14.49 KB	-rw-r--r--
tkinter.dnd.html	17.09 KB	-rw-r--r--
tkinter.font.html	22.21 KB	-rw-r--r--
tkinter.html	106.85 KB	-rw-r--r--
tkinter.messagebox.html	20.09 KB	-rw-r--r--
tkinter.scrolledtext.html	14.52 KB	-rw-r--r--
tkinter.tix.html	59.69 KB	-rw-r--r--
tkinter.ttk.html	138.37 KB	-rw-r--r--
token.html	45.73 KB	-rw-r--r--
tokenize.html	39.86 KB	-rw-r--r--
trace.html	38.85 KB	-rw-r--r--
traceback.html	75.61 KB	-rw-r--r--
tracemalloc.html	122.33 KB	-rw-r--r--
tty.html	14.46 KB	-rw-r--r--
turtle.html	271.71 KB	-rw-r--r--
types.html	64.85 KB	-rw-r--r--
typing.html	315.69 KB	-rw-r--r--
unicodedata.html	27.3 KB	-rw-r--r--
unittest.html	310.01 KB	-rw-r--r--
unittest.mock-examples.html	177.75 KB	-rw-r--r--
unittest.mock.html	363.51 KB	-rw-r--r--
unix.html	13.46 KB	-rw-r--r--
urllib.error.html	18.56 KB	-rw-r--r--
urllib.html	12.92 KB	-rw-r--r--
urllib.parse.html	104.65 KB	-rw-r--r--
urllib.request.html	208.87 KB	-rw-r--r--
urllib.robotparser.html	22.63 KB	-rw-r--r--
uu.html	18.2 KB	-rw-r--r--
uuid.html	42.88 KB	-rw-r--r--
venv.html	90.43 KB	-rw-r--r--
warnings.html	69.13 KB	-rw-r--r--
wave.html	36.12 KB	-rw-r--r--
weakref.html	73.36 KB	-rw-r--r--
webbrowser.html	33.98 KB	-rw-r--r--
windows.html	12.32 KB	-rw-r--r--
winreg.html	89.48 KB	-rw-r--r--
winsound.html	26.3 KB	-rw-r--r--
wsgiref.html	111.52 KB	-rw-r--r--
xdrlib.html	42.07 KB	-rw-r--r--
xml.dom.html	114.66 KB	-rw-r--r--
xml.dom.minidom.html	49.6 KB	-rw-r--r--
xml.dom.pulldom.html	30.06 KB	-rw-r--r--
xml.etree.elementtree.html	186.49 KB	-rw-r--r--
xml.html	22.34 KB	-rw-r--r--
xml.sax.handler.html	55.78 KB	-rw-r--r--
xml.sax.html	31.74 KB	-rw-r--r--
xml.sax.reader.html	56.23 KB	-rw-r--r--
xml.sax.utils.html	22.28 KB	-rw-r--r--
xmlrpc.client.html	79.73 KB	-rw-r--r--
xmlrpc.html	11.9 KB	-rw-r--r--
xmlrpc.server.html	63.56 KB	-rw-r--r--
zipapp.html	52.45 KB	-rw-r--r--
zipfile.html	116.59 KB	-rw-r--r--
zipimport.html	33.76 KB	-rw-r--r--
zlib.html	42.29 KB	-rw-r--r--
zoneinfo.html	57.25 KB	-rw-r--r--

Code Editor : struct.html

<!DOCTYPE html>

<title>struct — Interpret bytes as packed binary data &#8212; Python 3.10.12 documentation</title><meta name="viewport" content="width=device-width, initial-scale=1.0">
 
 <link rel="stylesheet" type="text/css" href="../_static/pygments.css" />
 <link rel="stylesheet" type="text/css" href="../_static/pydoctheme.css?2022.1" />
 
 <script data-url_root="../" id="documentation_options" src="../_static/documentation_options.js"></script>
 <script src="../_static/jquery.js"></script>
 <script src="../_static/underscore.js"></script>
 <script src="../_static/doctools.js"></script>
 
 <script src="../_static/sidebar.js"></script>
 
 <link rel="search" type="application/opensearchdescription+xml"
 title="Search within Python 3.10.12 documentation"
 href="../_static/opensearch.xml"/>
 <link rel="author" title="About these documents" href="../about.html" />
 <link rel="index" title="Index" href="../genindex.html" />
 <link rel="search" title="Search" href="../search.html" />
 <link rel="copyright" title="Copyright" href="../copyright.html" />
 <link rel="next" title="codecs — Codec registry and base classes" href="codecs.html" />
 <link rel="prev" title="Binary Data Services" href="binary.html" />
 <link rel="canonical" href="file:///usr/share/doc/python3.10/html/library/struct.html" />

</head>
<body>
<div class="mobile-nav">
 <input type="checkbox" id="menuToggler" class="toggler__input" aria-controls="navigation"
 aria-pressed="false" aria-expanded="false" role="button" aria-label="Menu" />
 <label for="menuToggler" class="toggler__label">
 
 </label>
 <nav class="nav-content" role="navigation">
 <a href="https://www.python.org/" class="nav-logo">
 <img src="../_static/py.svg" alt="Logo"/>
 </a>
 <div class="version_switcher_placeholder"></div>
 <form role="search" class="search" action="../search.html" method="get">
 <svg xmlns="http://www.w3.org/2000/svg" width="20" height="20" viewBox="0 0 24 24" class="search-icon">
 <path fill-rule="nonzero"
 d="M15.5 14h-.79l-.28-.27a6.5 6.5 0 001.48-5.34c-.47-2.78-2.79-5-5.59-5.34a6.505 6.505 0 00-7.27 7.27c.34 2.8 2.56 5.12 5.34 5.59a6.5 6.5 0 005.34-1.48l.27.28v.79l4.25 4.25c.41.41 1.08.41 1.49 0 .41-.41.41-1.08 0-1.49L15.5 14zm-6 0C7.01 14 5 11.99 5 9.5S7.01 5 9.5 5 14 7.01 14 9.5 11.99 14 9.5 14z" fill="#444"></path>
 </svg>
 <input type="text" name="q" aria-label="Quick search"/>
 <input type="submit" value="Go"/>
 </form>
 </nav>
 <div class="menu-wrapper">
 <nav class="menu" role="navigation" aria-label="main navigation">
 <div class="language_switcher_placeholder"></div>
 <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">struct</code> — Interpret bytes as packed binary data</a><ul>
<li><a class="reference internal" href="#functions-and-exceptions">Functions and Exceptions</a></li>
<li><a class="reference internal" href="#format-strings">Format Strings</a><ul>
<li><a class="reference internal" href="#byte-order-size-and-alignment">Byte Order, Size, and Alignment</a></li>
<li><a class="reference internal" href="#format-characters">Format Characters</a></li>
<li><a class="reference internal" href="#examples">Examples</a></li>
</ul>
</li>
<li><a class="reference internal" href="#applications">Applications</a><ul>
<li><a class="reference internal" href="#native-formats">Native Formats</a></li>
<li><a class="reference internal" href="#standard-formats">Standard Formats</a></li>
</ul>
</li>
<li><a class="reference internal" href="#classes">Classes</a></li>
</ul>
</li>
</ul>

<div class="related" role="navigation" aria-label="related navigation">
 <h3>Navigation</h3>
 <ul>
 <li class="right" style="margin-right: 10px">
 <a href="../genindex.html" title="General Index"
 accesskey="I">index</a></li>
 <li class="right" >
 <a href="../py-modindex.html" title="Python Module Index"
 >modules</a> |</li>
 <li class="right" >
 <a href="codecs.html" title="codecs — Codec registry and base classes"
 accesskey="N">next</a> |</li>
 <li class="right" >
 <a href="binary.html" title="Binary Data Services"
 accesskey="P">previous</a> |</li>

<li><img src="../_static/py.svg" alt="python logo" style="vertical-align: middle; margin-top: -1px"/></li>
 <li><a href="https://www.python.org/">Python</a> &#187;</li>
 <li class="switchers">
 <div class="language_switcher_placeholder"></div>
 <div class="version_switcher_placeholder"></div>
 </li>
 <li>
 
 </li>
 <li id="cpython-language-and-version">
 <a href="../index.html">3.10.12 Documentation</a> &#187;
 </li>

<li class="nav-item nav-item-1"><a href="index.html" >The Python Standard Library</a> &#187;</li>
 <li class="nav-item nav-item-2"><a href="binary.html" accesskey="U">Binary Data Services</a> &#187;</li>
 <li class="nav-item nav-item-this"><a href=""><code class="xref py py-mod docutils literal notranslate">struct</code> — Interpret bytes as packed binary data</a></li>
 <li class="right">

<div class="document">
 <div class="documentwrapper">
 <div class="bodywrapper">
 <div class="body" role="main">
 
 <section id="module-struct">
<h1><a class="reference internal" href="#module-struct" title="struct: Interpret bytes as packed binary data."><code class="xref py py-mod docutils literal notranslate">struct</code></a> — Interpret bytes as packed binary data<a class="headerlink" href="#module-struct" title="Permalink to this headline">¶</a></h1>
Source code: <a class="reference external" href="https://github.com/python/cpython/tree/3.10/Lib/struct.py">Lib/struct.py</a>
<hr class="docutils" id="index-0" />
This module converts between Python values and C structs represented
as Python <a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a> objects. Compact <a class="reference internal" href="#struct-format-strings">format strings</a>
describe the intended conversions to/from Python values.
The module’s functions and objects can be used for two largely
distinct applications, data exchange with external sources (files or
network connections), or data transfer between the Python application
and the C layer.
<div class="admonition note">
Note
When no prefix character is given, native mode is the default. It
packs or unpacks data based on the platform and compiler on which
the Python interpreter was built.
The result of packing a given C struct includes pad bytes which
maintain proper alignment for the C types involved; similarly,
alignment is taken into account when unpacking. In contrast, when
communicating data between external sources, the programmer is
responsible for defining byte ordering and padding between elements.
See <a class="reference internal" href="#struct-alignment">Byte Order, Size, and Alignment</a> for details.
</div>
Several <a class="reference internal" href="#module-struct" title="struct: Interpret bytes as packed binary data."><code class="xref py py-mod docutils literal notranslate">struct</code></a> functions (and methods of <a class="reference internal" href="#struct.Struct" title="struct.Struct"><code class="xref py py-class docutils literal notranslate">Struct</code></a>) take a buffer
argument. This refers to objects that implement the <a class="reference internal" href="../c-api/buffer.html#bufferobjects">Buffer Protocol</a> and
provide either a readable or read-writable buffer. The most common types used
for that purpose are <a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a> and <a class="reference internal" href="stdtypes.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate">bytearray</code></a>, but many other types
that can be viewed as an array of bytes implement the buffer protocol, so that
they can be read/filled without additional copying from a <a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a> object.
<section id="functions-and-exceptions">
<h2>Functions and Exceptions<a class="headerlink" href="#functions-and-exceptions" title="Permalink to this headline">¶</a></h2>
The module defines the following exception and functions:
<dl class="py exception">
<dt class="sig sig-object py" id="struct.error">
exception struct.error<a class="headerlink" href="#struct.error" title="Permalink to this definition">¶</a></dt>
<dd>Exception raised on various occasions; argument is a string describing what
is wrong.
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="struct.pack">
struct.pack(format, v1, v2, ...)<a class="headerlink" href="#struct.pack" title="Permalink to this definition">¶</a></dt>
<dd>Return a bytes object containing the values v1, v2, … packed according
to the format string format. The arguments must match the values required by
the format exactly.
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="struct.pack_into">
struct.pack_into(format, buffer, offset, v1, v2, ...)<a class="headerlink" href="#struct.pack_into" title="Permalink to this definition">¶</a></dt>
<dd>Pack the values v1, v2, … according to the format string format and
write the packed bytes into the writable buffer buffer starting at
position offset. Note that offset is a required argument.
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="struct.unpack">
struct.unpack(format, buffer)<a class="headerlink" href="#struct.unpack" title="Permalink to this definition">¶</a></dt>
<dd>Unpack from the buffer buffer (presumably packed by <code class="docutils literal notranslate">pack(format, ...)</code>)
according to the format string format. The result is a tuple even if it
contains exactly one item. The buffer’s size in bytes must match the
size required by the format, as reflected by <a class="reference internal" href="#struct.calcsize" title="struct.calcsize"><code class="xref py py-func docutils literal notranslate">calcsize()</code></a>.
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="struct.unpack_from">
struct.unpack_from(format, /, buffer, offset=0)<a class="headerlink" href="#struct.unpack_from" title="Permalink to this definition">¶</a></dt>
<dd>Unpack from buffer starting at position offset, according to the format
string format. The result is a tuple even if it contains exactly one
item. The buffer’s size in bytes, starting at position offset, must be at
least the size required by the format, as reflected by <a class="reference internal" href="#struct.calcsize" title="struct.calcsize"><code class="xref py py-func docutils literal notranslate">calcsize()</code></a>.
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="struct.iter_unpack">
struct.iter_unpack(format, buffer)<a class="headerlink" href="#struct.iter_unpack" title="Permalink to this definition">¶</a></dt>
<dd>Iteratively unpack from the buffer buffer according to the format
string format. This function returns an iterator which will read
equally sized chunks from the buffer until all its contents have been
consumed. The buffer’s size in bytes must be a multiple of the size
required by the format, as reflected by <a class="reference internal" href="#struct.calcsize" title="struct.calcsize"><code class="xref py py-func docutils literal notranslate">calcsize()</code></a>.
Each iteration yields a tuple as specified by the format string.
<div class="versionadded">
New in version 3.4.
</div>
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="struct.calcsize">
struct.calcsize(format)<a class="headerlink" href="#struct.calcsize" title="Permalink to this definition">¶</a></dt>
<dd>Return the size of the struct (and hence of the bytes object produced by
<code class="docutils literal notranslate">pack(format, ...)</code>) corresponding to the format string format.
</dd></dl>

</section>
<section id="format-strings">
<h2>Format Strings<a class="headerlink" href="#format-strings" title="Permalink to this headline">¶</a></h2>
Format strings describe the data layout when
packing and unpacking data. They are built up from <a class="reference internal" href="#format-characters">format characters</a>,
which specify the type of data being packed/unpacked. In addition,
special characters control the <a class="reference internal" href="#struct-alignment">byte order, size and alignment</a>.
Each format string consists of an optional prefix character which
describes the overall properties of the data and one or more format
characters which describe the actual data values and padding.
<section id="byte-order-size-and-alignment">
<h3>Byte Order, Size, and Alignment<a class="headerlink" href="#byte-order-size-and-alignment" title="Permalink to this headline">¶</a></h3>
By default, C types are represented in the machine’s native format and byte
order, and properly aligned by skipping pad bytes if necessary (according to the
rules used by the C compiler).
This behavior is chosen so
that the bytes of a packed struct correspond exactly to the memory layout
of the corresponding C struct.
Whether to use native byte ordering
and padding or standard formats depends on the application.
Alternatively, the first character of the format string can be used to indicate
the byte order, size and alignment of the packed data, according to the
following table:
<table class="docutils align-default">
<colgroup>
<col style="width: 20%" />
<col style="width: 43%" />
<col style="width: 18%" />
<col style="width: 20%" />
</colgroup>
<thead>
<tr class="row-odd"><th class="head">Character</th>
<th class="head">Byte order</th>
<th class="head">Size</th>
<th class="head">Alignment</th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><code class="docutils literal notranslate">&#64;</code></td>
<td>native</td>
<td>native</td>
<td>native</td>
</tr>
<tr class="row-odd"><td><code class="docutils literal notranslate">=</code></td>
<td>native</td>
<td>standard</td>
<td>none</td>
</tr>
<tr class="row-even"><td><code class="docutils literal notranslate">&lt;</code></td>
<td>little-endian</td>
<td>standard</td>
<td>none</td>
</tr>
<tr class="row-odd"><td><code class="docutils literal notranslate">&gt;</code></td>
<td>big-endian</td>
<td>standard</td>
<td>none</td>
</tr>
<tr class="row-even"><td><code class="docutils literal notranslate">!</code></td>
<td>network (= big-endian)</td>
<td>standard</td>
<td>none</td>
</tr>
</tbody>
</table>
If the first character is not one of these, <code class="docutils literal notranslate">'&#64;'</code> is assumed.
Native byte order is big-endian or little-endian, depending on the
host system. For example, Intel x86, AMD64 (x86-64), and Apple M1 are
little-endian; IBM z and many legacy architectures are big-endian.
Use <a class="reference internal" href="sys.html#sys.byteorder" title="sys.byteorder"><code class="xref py py-data docutils literal notranslate">sys.byteorder</code></a> to check the endianness of your system.
Native size and alignment are determined using the C compiler’s
<code class="docutils literal notranslate">sizeof</code> expression. This is always combined with native byte order.
Standard size depends only on the format character; see the table in
the <a class="reference internal" href="#format-characters">Format Characters</a> section.
Note the difference between <code class="docutils literal notranslate">'&#64;'</code> and <code class="docutils literal notranslate">'='</code>: both use native byte order, but
the size and alignment of the latter is standardized.
The form <code class="docutils literal notranslate">'!'</code> represents the network byte order which is always big-endian
as defined in <a class="reference external" href="https://tools.ietf.org/html/rfc1700">IETF RFC 1700</a>.
There is no way to indicate non-native byte order (force byte-swapping); use the
appropriate choice of <code class="docutils literal notranslate">'&lt;'</code> or <code class="docutils literal notranslate">'&gt;'</code>.
Notes:
<ol class="arabic simple">
<li>Padding is only automatically added between successive structure members.
No padding is added at the beginning or the end of the encoded struct.</li>
<li>No padding is added when using non-native size and alignment, e.g.
with ‘&lt;’, ‘&gt;’, ‘=’, and ‘!’.</li>
<li>To align the end of a structure to the alignment requirement of a
particular type, end the format with the code for that type with a repeat
count of zero. See <a class="reference internal" href="#struct-examples">Examples</a>.</li>
</ol>
</section>
<section id="format-characters">
<h3>Format Characters<a class="headerlink" href="#format-characters" title="Permalink to this headline">¶</a></h3>
Format characters have the following meaning; the conversion between C and
Python values should be obvious given their types. The ‘Standard size’ column
refers to the size of the packed value in bytes when using standard size; that
is, when the format string starts with one of <code class="docutils literal notranslate">'&lt;'</code>, <code class="docutils literal notranslate">'&gt;'</code>, <code class="docutils literal notranslate">'!'</code> or
<code class="docutils literal notranslate">'='</code>. When using native size, the size of the packed value is
platform-dependent.
<table class="docutils align-default">
<colgroup>
<col style="width: 10%" />
<col style="width: 32%" />
<col style="width: 24%" />
<col style="width: 20%" />
<col style="width: 15%" />
</colgroup>
<thead>
<tr class="row-odd"><th class="head">Format</th>
<th class="head">C Type</th>
<th class="head">Python type</th>
<th class="head">Standard size</th>
<th class="head">Notes</th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><code class="docutils literal notranslate">x</code></td>
<td>pad byte</td>
<td>no value</td>
<td></td>
<td>(7)</td>
</tr>
<tr class="row-odd"><td><code class="docutils literal notranslate">c</code></td>
<td>char</td>
<td>bytes of length 1</td>
<td>1</td>
<td></td>
</tr>
<tr class="row-even"><td><code class="docutils literal notranslate">b</code></td>
<td>signed char</td>
<td>integer</td>
<td>1</td>
<td>(1), (2)</td>
</tr>
<tr class="row-odd"><td><code class="docutils literal notranslate">B</code></td>
<td>unsigned char</td>
<td>integer</td>
<td>1</td>
<td>(2)</td>
</tr>
<tr class="row-even"><td><code class="docutils literal notranslate">?</code></td>
<td>_Bool</td>
<td>bool</td>
<td>1</td>
<td>(1)</td>
</tr>
<tr class="row-odd"><td><code class="docutils literal notranslate">h</code></td>
<td>short</td>
<td>integer</td>
<td>2</td>
<td>(2)</td>
</tr>
<tr class="row-even"><td><code class="docutils literal notranslate">H</code></td>
<td>unsigned short</td>
<td>integer</td>
<td>2</td>
<td>(2)</td>
</tr>
<tr class="row-odd"><td><code class="docutils literal notranslate">i</code></td>
<td>int</td>
<td>integer</td>
<td>4</td>
<td>(2)</td>
</tr>
<tr class="row-even"><td><code class="docutils literal notranslate">I</code></td>
<td>unsigned int</td>
<td>integer</td>
<td>4</td>
<td>(2)</td>
</tr>
<tr class="row-odd"><td><code class="docutils literal notranslate">l</code></td>
<td>long</td>
<td>integer</td>
<td>4</td>
<td>(2)</td>
</tr>
<tr class="row-even"><td><code class="docutils literal notranslate">L</code></td>
<td>unsigned long</td>
<td>integer</td>
<td>4</td>
<td>(2)</td>
</tr>
<tr class="row-odd"><td><code class="docutils literal notranslate">q</code></td>
<td>long long</td>
<td>integer</td>
<td>8</td>
<td>(2)</td>
</tr>
<tr class="row-even"><td><code class="docutils literal notranslate">Q</code></td>
<td>unsigned long long</td>
<td>integer</td>
<td>8</td>
<td>(2)</td>
</tr>
<tr class="row-odd"><td><code class="docutils literal notranslate">n</code></td>
<td>ssize_t</td>
<td>integer</td>
<td></td>
<td>(3)</td>
</tr>
<tr class="row-even"><td><code class="docutils literal notranslate">N</code></td>
<td>size_t</td>
<td>integer</td>
<td></td>
<td>(3)</td>
</tr>
<tr class="row-odd"><td><code class="docutils literal notranslate">e</code></td>
<td>(6)</td>
<td>float</td>
<td>2</td>
<td>(4)</td>
</tr>
<tr class="row-even"><td><code class="docutils literal notranslate">f</code></td>
<td>float</td>
<td>float</td>
<td>4</td>
<td>(4)</td>
</tr>
<tr class="row-odd"><td><code class="docutils literal notranslate">d</code></td>
<td>double</td>
<td>float</td>
<td>8</td>
<td>(4)</td>
</tr>
<tr class="row-even"><td><code class="docutils literal notranslate">s</code></td>
<td>char[]</td>
<td>bytes</td>
<td></td>
<td>(9)</td>
</tr>
<tr class="row-odd"><td><code class="docutils literal notranslate">p</code></td>
<td>char[]</td>
<td>bytes</td>
<td></td>
<td>(8)</td>
</tr>
<tr class="row-even"><td><code class="docutils literal notranslate">P</code></td>
<td>void*</td>
<td>integer</td>
<td></td>
<td>(5)</td>
</tr>
</tbody>
</table>
<div class="versionchanged">
Changed in version 3.3: Added support for the <code class="docutils literal notranslate">'n'</code> and <code class="docutils literal notranslate">'N'</code> formats.
</div>
<div class="versionchanged">
Changed in version 3.6: Added support for the <code class="docutils literal notranslate">'e'</code> format.
</div>
Notes:
<ol class="arabic">
<li>The <code class="docutils literal notranslate">'?'</code> conversion code corresponds to the _Bool type defined by
C99. If this type is not available, it is simulated using a char. In
standard mode, it is always represented by one byte.
</li>
<li>When attempting to pack a non-integer using any of the integer conversion
codes, if the non-integer has a <code class="xref py py-meth docutils literal notranslate">__index__()</code> method then that method is
called to convert the argument to an integer before packing.
<div class="versionchanged">
Changed in version 3.2: Added use of the <code class="xref py py-meth docutils literal notranslate">__index__()</code> method for non-integers.
</div>
</li>
<li>The <code class="docutils literal notranslate">'n'</code> and <code class="docutils literal notranslate">'N'</code> conversion codes are only available for the native
size (selected as the default or with the <code class="docutils literal notranslate">'&#64;'</code> byte order character).
For the standard size, you can use whichever of the other integer formats
fits your application.</li>
<li>For the <code class="docutils literal notranslate">'f'</code>, <code class="docutils literal notranslate">'d'</code> and <code class="docutils literal notranslate">'e'</code> conversion codes, the packed
representation uses the IEEE 754 binary32, binary64 or binary16 format (for
<code class="docutils literal notranslate">'f'</code>, <code class="docutils literal notranslate">'d'</code> or <code class="docutils literal notranslate">'e'</code> respectively), regardless of the floating-point
format used by the platform.</li>
<li>The <code class="docutils literal notranslate">'P'</code> format character is only available for the native byte ordering
(selected as the default or with the <code class="docutils literal notranslate">'&#64;'</code> byte order character). The byte
order character <code class="docutils literal notranslate">'='</code> chooses to use little- or big-endian ordering based
on the host system. The struct module does not interpret this as native
ordering, so the <code class="docutils literal notranslate">'P'</code> format is not available.</li>
<li>The IEEE 754 binary16 “half precision” type was introduced in the 2008
revision of the <a class="reference external" href="https://en.wikipedia.org/wiki/IEEE_754-2008_revision">IEEE 754 standard</a>. It has a sign
bit, a 5-bit exponent and 11-bit precision (with 10 bits explicitly stored),
and can represent numbers between approximately <code class="docutils literal notranslate">6.1e-05</code> and <code class="docutils literal notranslate">6.5e+04</code>
at full precision. This type is not widely supported by C compilers: on a
typical machine, an unsigned short can be used for storage, but not for math
operations. See the Wikipedia page on the <a class="reference external" href="https://en.wikipedia.org/wiki/Half-precision_floating-point_format">half-precision floating-point
format</a> for more information.</li>
<li>When packing, <code class="docutils literal notranslate">'x'</code> inserts one NUL byte.</li>
<li>The <code class="docutils literal notranslate">'p'</code> format character encodes a “Pascal string”, meaning a short
variable-length string stored in a fixed number of bytes, given by the count.
The first byte stored is the length of the string, or 255, whichever is
smaller. The bytes of the string follow. If the string passed in to
<a class="reference internal" href="#struct.pack" title="struct.pack"><code class="xref py py-func docutils literal notranslate">pack()</code></a> is too long (longer than the count minus 1), only the leading
<code class="docutils literal notranslate">count-1</code> bytes of the string are stored. If the string is shorter than
<code class="docutils literal notranslate">count-1</code>, it is padded with null bytes so that exactly count bytes in all
are used. Note that for <a class="reference internal" href="#struct.unpack" title="struct.unpack"><code class="xref py py-func docutils literal notranslate">unpack()</code></a>, the <code class="docutils literal notranslate">'p'</code> format character consumes
<code class="docutils literal notranslate">count</code> bytes, but that the string returned can never contain more than 255
bytes.</li>
<li>For the <code class="docutils literal notranslate">'s'</code> format character, the count is interpreted as the length of the
bytes, not a repeat count like for the other format characters; for example,
<code class="docutils literal notranslate">'10s'</code> means a single 10-byte string mapping to or from a single
Python byte string, while <code class="docutils literal notranslate">'10c'</code> means 10
separate one byte character elements (e.g., <code class="docutils literal notranslate">cccccccccc</code>) mapping
to or from ten different Python byte objects. (See <a class="reference internal" href="#struct-examples">Examples</a>
for a concrete demonstration of the difference.)
If a count is not given, it defaults to 1. For packing, the string is
truncated or padded with null bytes as appropriate to make it fit. For
unpacking, the resulting bytes object always has exactly the specified number
of bytes. As a special case, <code class="docutils literal notranslate">'0s'</code> means a single, empty string (while
<code class="docutils literal notranslate">'0c'</code> means 0 characters).</li>
</ol>
A format character may be preceded by an integral repeat count. For example,
the format string <code class="docutils literal notranslate">'4h'</code> means exactly the same as <code class="docutils literal notranslate">'hhhh'</code>.
Whitespace characters between formats are ignored; a count and its format must
not contain whitespace though.
When packing a value <code class="docutils literal notranslate">x</code> using one of the integer formats (<code class="docutils literal notranslate">'b'</code>,
<code class="docutils literal notranslate">'B'</code>, <code class="docutils literal notranslate">'h'</code>, <code class="docutils literal notranslate">'H'</code>, <code class="docutils literal notranslate">'i'</code>, <code class="docutils literal notranslate">'I'</code>, <code class="docutils literal notranslate">'l'</code>, <code class="docutils literal notranslate">'L'</code>,
<code class="docutils literal notranslate">'q'</code>, <code class="docutils literal notranslate">'Q'</code>), if <code class="docutils literal notranslate">x</code> is outside the valid range for that format
then <a class="reference internal" href="#struct.error" title="struct.error"><code class="xref py py-exc docutils literal notranslate">struct.error</code></a> is raised.
<div class="versionchanged">
Changed in version 3.1: Previously, some of the integer formats wrapped out-of-range values and
raised <a class="reference internal" href="exceptions.html#DeprecationWarning" title="DeprecationWarning"><code class="xref py py-exc docutils literal notranslate">DeprecationWarning</code></a> instead of <a class="reference internal" href="#struct.error" title="struct.error"><code class="xref py py-exc docutils literal notranslate">struct.error</code></a>.
</div>
For the <code class="docutils literal notranslate">'?'</code> format character, the return value is either <a class="reference internal" href="constants.html#True" title="True"><code class="xref py py-const docutils literal notranslate">True</code></a> or
<a class="reference internal" href="constants.html#False" title="False"><code class="xref py py-const docutils literal notranslate">False</code></a>. When packing, the truth value of the argument object is used.
Either 0 or 1 in the native or standard bool representation will be packed, and
any non-zero value will be <code class="docutils literal notranslate">True</code> when unpacking.
</section>
<section id="examples">
<h3>Examples<a class="headerlink" href="#examples" title="Permalink to this headline">¶</a></h3>
<div class="admonition note">
Note
Native byte order examples (designated by the <code class="docutils literal notranslate">'&#64;'</code> format prefix or
lack of any prefix character) may not match what the reader’s
machine produces as
that depends on the platform and compiler.
</div>
Pack and unpack integers of three different sizes, using big endian
ordering:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; from struct import *
&gt;&gt;&gt; pack(&quot;&gt;bhl&quot;, 1, 2, 3)
b&#39;\x01\x00\x02\x00\x00\x00\x03&#39;
&gt;&gt;&gt; unpack(&#39;&gt;bhl&#39;, b&#39;\x01\x00\x02\x00\x00\x00\x03&#39;)
(1, 2, 3)
&gt;&gt;&gt; calcsize(&#39;&gt;bhl&#39;)
7
</pre></div>
</div>
Attempt to pack an integer which is too large for the defined field:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; pack(&quot;&gt;h&quot;, 99999)
Traceback (most recent call last):
 File &quot;&lt;stdin&gt;&quot;, line 1, in &lt;module&gt;
struct.error: &#39;h&#39; format requires -32768 &lt;= number &lt;= 32767
</pre></div>
</div>
Demonstrate the difference between <code class="docutils literal notranslate">'s'</code> and <code class="docutils literal notranslate">'c'</code> format
characters:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; pack(&quot;@ccc&quot;, b&#39;1&#39;, b&#39;2&#39;, b&#39;3&#39;)
b&#39;123&#39;
&gt;&gt;&gt; pack(&quot;@3s&quot;, b&#39;123&#39;)
b&#39;123&#39;
</pre></div>
</div>
Unpacked fields can be named by assigning them to variables or by wrapping
the result in a named tuple:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; record = b&#39;raymond \x32\x12\x08\x01\x08&#39;
&gt;&gt;&gt; name, serialnum, school, gradelevel = unpack(&#39;&lt;10sHHb&#39;, record)

&gt;&gt;&gt; from collections import namedtuple
&gt;&gt;&gt; Student = namedtuple(&#39;Student&#39;, &#39;name serialnum school gradelevel&#39;)
&gt;&gt;&gt; Student._make(unpack(&#39;&lt;10sHHb&#39;, record))
Student(name=b&#39;raymond &#39;, serialnum=4658, school=264, gradelevel=8)
</pre></div>
</div>
The ordering of format characters may have an impact on size in native
mode since padding is implicit. In standard mode, the user is
responsible for inserting any desired padding.
Note in
the first <code class="docutils literal notranslate">pack</code> call below that three NUL bytes were added after the
packed <code class="docutils literal notranslate">'#'</code> to align the following integer on a four-byte boundary.
In this example, the output was produced on a little endian machine:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; pack(&#39;@ci&#39;, b&#39;#&#39;, 0x12131415)
b&#39;#\x00\x00\x00\x15\x14\x13\x12&#39;
&gt;&gt;&gt; pack(&#39;@ic&#39;, 0x12131415, b&#39;#&#39;)
b&#39;\x15\x14\x13\x12#&#39;
&gt;&gt;&gt; calcsize(&#39;@ci&#39;)
8
&gt;&gt;&gt; calcsize(&#39;@ic&#39;)
5
</pre></div>
</div>
The following format <code class="docutils literal notranslate">'llh0l'</code> results in two pad bytes being added
at the end, assuming the platform’s longs are aligned on 4-byte boundaries:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; pack(&#39;@llh0l&#39;, 1, 2, 3)
b&#39;\x00\x00\x00\x01\x00\x00\x00\x02\x00\x03\x00\x00&#39;
</pre></div>
</div>
<div class="admonition seealso">
See also
<dl class="simple">
<dt>Module <a class="reference internal" href="array.html#module-array" title="array: Space efficient arrays of uniformly typed numeric values."><code class="xref py py-mod docutils literal notranslate">array</code></a></dt><dd>Packed binary storage of homogeneous data.
</dd>
<dt>Module <a class="reference internal" href="json.html#module-json" title="json: Encode and decode the JSON format."><code class="xref py py-mod docutils literal notranslate">json</code></a></dt><dd>JSON encoder and decoder.
</dd>
<dt>Module <a class="reference internal" href="pickle.html#module-pickle" title="pickle: Convert Python objects to streams of bytes and back."><code class="xref py py-mod docutils literal notranslate">pickle</code></a></dt><dd>Python object serialization.
</dd>
</dl>
</div>
</section>
</section>
<section id="applications">
<h2>Applications<a class="headerlink" href="#applications" title="Permalink to this headline">¶</a></h2>
Two main applications for the <a class="reference internal" href="#module-struct" title="struct: Interpret bytes as packed binary data."><code class="xref py py-mod docutils literal notranslate">struct</code></a> module exist, data
interchange between Python and C code within an application or another
application compiled using the same compiler (<a class="reference internal" href="#struct-native-formats">native formats</a>), and
data interchange between applications using agreed upon data layout
(<a class="reference internal" href="#struct-standard-formats">standard formats</a>). Generally speaking, the format strings
constructed for these two domains are distinct.
<section id="native-formats">
<h3>Native Formats<a class="headerlink" href="#native-formats" title="Permalink to this headline">¶</a></h3>
When constructing format strings which mimic native layouts, the
compiler and machine architecture determine byte ordering and padding.
In such cases, the <code class="docutils literal notranslate">&#64;</code> format character should be used to specify
native byte ordering and data sizes. Internal pad bytes are normally inserted
automatically. It is possible that a zero-repeat format code will be
needed at the end of a format string to round up to the correct
byte boundary for proper alignment of consective chunks of data.
Consider these two simple examples (on a 64-bit, little-endian
machine):
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; calcsize(&#39;@lhl&#39;)
24
&gt;&gt;&gt; calcsize(&#39;@llh&#39;)
18
</pre></div>
</div>
Data is not padded to an 8-byte boundary at the end of the second
format string without the use of extra padding. A zero-repeat format
code solves that problem:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; calcsize(&#39;@llh0l&#39;)
24
</pre></div>
</div>
The <code class="docutils literal notranslate">'x'</code> format code can be used to specify the repeat, but for
native formats it is better to use a zero-repeat format like <code class="docutils literal notranslate">'0l'</code>.
By default, native byte ordering and alignment is used, but it is
better to be explicit and use the <code class="docutils literal notranslate">'&#64;'</code> prefix character.
</section>
<section id="standard-formats">
<h3>Standard Formats<a class="headerlink" href="#standard-formats" title="Permalink to this headline">¶</a></h3>
When exchanging data beyond your process such as networking or storage,
be precise. Specify the exact byte order, size, and alignment. Do
not assume they match the native order of a particular machine.
For example, network byte order is big-endian, while many popular CPUs
are little-endian. By defining this explicitly, the user need not
care about the specifics of the platform their code is running on.
The first character should typically be <code class="docutils literal notranslate">&lt;</code> or <code class="docutils literal notranslate">&gt;</code>
(or <code class="docutils literal notranslate">!</code>). Padding is the responsibility of the programmer. The
zero-repeat format character won’t work. Instead, the user must
explicitly add <code class="docutils literal notranslate">'x'</code> pad bytes where needed. Revisiting the
examples from the previous section, we have:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; calcsize(&#39;&lt;qh6xq&#39;)
24
&gt;&gt;&gt; pack(&#39;&lt;qh6xq&#39;, 1, 2, 3) == pack(&#39;@lhl&#39;, 1, 2, 3)
True
&gt;&gt;&gt; calcsize(&#39;@llh&#39;)
18
&gt;&gt;&gt; pack(&#39;@llh&#39;, 1, 2, 3) == pack(&#39;&lt;qqh&#39;, 1, 2, 3)
True
&gt;&gt;&gt; calcsize(&#39;&lt;qqh6x&#39;)
24
&gt;&gt;&gt; calcsize(&#39;@llh0l&#39;)
24
&gt;&gt;&gt; pack(&#39;@llh0l&#39;, 1, 2, 3) == pack(&#39;&lt;qqh6x&#39;, 1, 2, 3)
True
</pre></div>
</div>
The above results (executed on a 64-bit machine) aren’t guaranteed to
match when executed on different machines. For example, the examples
below were executed on a 32-bit machine:
<div class="highlight-python3 notranslate"><div class="highlight"><pre>&gt;&gt;&gt; calcsize(&#39;&lt;qqh6x&#39;)
24
&gt;&gt;&gt; calcsize(&#39;@llh0l&#39;)
12
&gt;&gt;&gt; pack(&#39;@llh0l&#39;, 1, 2, 3) == pack(&#39;&lt;qqh6x&#39;, 1, 2, 3)
False
</pre></div>
</div>
</section>
</section>
<section id="classes">
<h2>Classes<a class="headerlink" href="#classes" title="Permalink to this headline">¶</a></h2>
The <a class="reference internal" href="#module-struct" title="struct: Interpret bytes as packed binary data."><code class="xref py py-mod docutils literal notranslate">struct</code></a> module also defines the following type:
<dl class="py class">
<dt class="sig sig-object py" id="struct.Struct">
class struct.Struct(format)<a class="headerlink" href="#struct.Struct" title="Permalink to this definition">¶</a></dt>
<dd>Return a new Struct object which writes and reads binary data according to
the format string format. Creating a <code class="docutils literal notranslate">Struct</code> object once and calling its
methods is more efficient than calling module-level functions with the
same format since the format string is only compiled once.
<div class="admonition note">
Note
The compiled versions of the most recent format strings passed to
<a class="reference internal" href="#struct.Struct" title="struct.Struct"><code class="xref py py-class docutils literal notranslate">Struct</code></a> and the module-level functions are cached, so programs
that use only a few format strings needn’t worry about reusing a single
<a class="reference internal" href="#struct.Struct" title="struct.Struct"><code class="xref py py-class docutils literal notranslate">Struct</code></a> instance.
</div>
Compiled Struct objects support the following methods and attributes:
<dl class="py method">
<dt class="sig sig-object py" id="struct.Struct.pack">
pack(v1, v2, ...)<a class="headerlink" href="#struct.Struct.pack" title="Permalink to this definition">¶</a></dt>
<dd>Identical to the <a class="reference internal" href="#struct.pack" title="struct.pack"><code class="xref py py-func docutils literal notranslate">pack()</code></a> function, using the compiled format.
(<code class="docutils literal notranslate">len(result)</code> will equal <a class="reference internal" href="#struct.Struct.size" title="struct.Struct.size"><code class="xref py py-attr docutils literal notranslate">size</code></a>.)
</dd></dl>

<dl class="py method">
<dt class="sig sig-object py" id="struct.Struct.pack_into">
pack_into(buffer, offset, v1, v2, ...)<a class="headerlink" href="#struct.Struct.pack_into" title="Permalink to this definition">¶</a></dt>
<dd>Identical to the <a class="reference internal" href="#struct.pack_into" title="struct.pack_into"><code class="xref py py-func docutils literal notranslate">pack_into()</code></a> function, using the compiled format.
</dd></dl>

<dl class="py method">
<dt class="sig sig-object py" id="struct.Struct.unpack">
unpack(buffer)<a class="headerlink" href="#struct.Struct.unpack" title="Permalink to this definition">¶</a></dt>
<dd>Identical to the <a class="reference internal" href="#struct.unpack" title="struct.unpack"><code class="xref py py-func docutils literal notranslate">unpack()</code></a> function, using the compiled format.
The buffer’s size in bytes must equal <a class="reference internal" href="#struct.Struct.size" title="struct.Struct.size"><code class="xref py py-attr docutils literal notranslate">size</code></a>.
</dd></dl>

<dl class="py method">
<dt class="sig sig-object py" id="struct.Struct.unpack_from">
unpack_from(buffer, offset=0)<a class="headerlink" href="#struct.Struct.unpack_from" title="Permalink to this definition">¶</a></dt>
<dd>Identical to the <a class="reference internal" href="#struct.unpack_from" title="struct.unpack_from"><code class="xref py py-func docutils literal notranslate">unpack_from()</code></a> function, using the compiled format.
The buffer’s size in bytes, starting at position offset, must be at least
<a class="reference internal" href="#struct.Struct.size" title="struct.Struct.size"><code class="xref py py-attr docutils literal notranslate">size</code></a>.
</dd></dl>

<dl class="py method">
<dt class="sig sig-object py" id="struct.Struct.iter_unpack">
iter_unpack(buffer)<a class="headerlink" href="#struct.Struct.iter_unpack" title="Permalink to this definition">¶</a></dt>
<dd>Identical to the <a class="reference internal" href="#struct.iter_unpack" title="struct.iter_unpack"><code class="xref py py-func docutils literal notranslate">iter_unpack()</code></a> function, using the compiled format.
The buffer’s size in bytes must be a multiple of <a class="reference internal" href="#struct.Struct.size" title="struct.Struct.size"><code class="xref py py-attr docutils literal notranslate">size</code></a>.
<div class="versionadded">
New in version 3.4.
</div>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="struct.Struct.format">
format<a class="headerlink" href="#struct.Struct.format" title="Permalink to this definition">¶</a></dt>
<dd>The format string used to construct this Struct object.
<div class="versionchanged">
Changed in version 3.7: The format string type is now <a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> instead of <a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a>.
</div>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="struct.Struct.size">
size<a class="headerlink" href="#struct.Struct.size" title="Permalink to this definition">¶</a></dt>
<dd>The calculated size of the struct (and hence of the bytes object produced
by the <a class="reference internal" href="#struct.pack" title="struct.pack"><code class="xref py py-meth docutils literal notranslate">pack()</code></a> method) corresponding to <a class="reference internal" href="functions.html#format" title="format"><code class="xref py py-attr docutils literal notranslate">format</code></a>.
</dd></dl>

</dd></dl>

</section>
</section>

<div class="clearer"></div>
 </div>
 </div>
 </div>
 <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">struct</code> — Interpret bytes as packed binary data</a><ul>
<li><a class="reference internal" href="#functions-and-exceptions">Functions and Exceptions</a></li>
<li><a class="reference internal" href="#format-strings">Format Strings</a><ul>
<li><a class="reference internal" href="#byte-order-size-and-alignment">Byte Order, Size, and Alignment</a></li>
<li><a class="reference internal" href="#format-characters">Format Characters</a></li>
<li><a class="reference internal" href="#examples">Examples</a></li>
</ul>
</li>
<li><a class="reference internal" href="#applications">Applications</a><ul>
<li><a class="reference internal" href="#native-formats">Native Formats</a></li>
<li><a class="reference internal" href="#standard-formats">Standard Formats</a></li>
</ul>
</li>
<li><a class="reference internal" href="#classes">Classes</a></li>
</ul>
</li>
</ul>

<h4>Previous topic</h4>
 <a href="binary.html"
 title="previous chapter">Binary Data Services</a>
 <h4>Next topic</h4>
 <a href="codecs.html"
 title="next chapter"><code class="xref py py-mod docutils literal notranslate">codecs</code> — Codec registry and base classes</a>
 <div role="note" aria-label="source link">
 <h3>This Page</h3>
 <ul class="this-page-menu">
 <li><a href="../bugs.html">Report a Bug</a></li>
 <li>
 <a href="https://github.com/python/cpython/blob/3.10/Doc/library/struct.rst"
 rel="nofollow">Show Source
 </a>
 </li>
 </ul>
 </div>
 </div>
 </div>
 <div class="clearer"></div>
 </div> 
 <div class="related" role="navigation" aria-label="related navigation">
 <h3>Navigation</h3>
 <ul>
 <li class="right" style="margin-right: 10px">
 <a href="../genindex.html" title="General Index"
 >index</a></li>
 <li class="right" >
 <a href="../py-modindex.html" title="Python Module Index"
 >modules</a> |</li>
 <li class="right" >
 <a href="codecs.html" title="codecs — Codec registry and base classes"
 >next</a> |</li>
 <li class="right" >
 <a href="binary.html" title="Binary Data Services"
 >previous</a> |</li>

<li class="nav-item nav-item-1"><a href="index.html" >The Python Standard Library</a> &#187;</li>
 <li class="nav-item nav-item-2"><a href="binary.html" >Binary Data Services</a> &#187;</li>
 <li class="nav-item nav-item-this"><a href=""><code class="xref py py-mod docutils literal notranslate">struct</code> — Interpret bytes as packed binary data</a></li>
 <li class="right">

<div class="inline-search" role="search">
 <form class="inline-search" action="../search.html" method="get">
 <input placeholder="Quick search" aria-label="Quick search" type="text" name="q" />
 <input type="submit" value="Go" />
 <input type="hidden" name="check_keywords" value="yes" />
 <input type="hidden" name="area" value="default" />
 </form>
 </div>
 |
 </li>
 
 </ul>
 </div> 
 <div class="footer">
 &copy; <a href="../copyright.html">Copyright</a> 2001-2026, Python Software Foundation.
 
 This page is licensed under the Python Software Foundation License Version 2.
 
 Examples, recipes, and other code in the documentation are additionally licensed under the Zero Clause BSD License.
 
 See <a href="/license.html">History and License</a> for more information.

The Python Software Foundation is a non-profit corporation.
<a href="https://www.python.org/psf/donations/">Please donate.</a>

Last updated on January 26, 2026.
 <a href="/bugs.html">Found a bug</a>?

Created using <a href="https://www.sphinx-doc.org/">Sphinx</a> 4.3.2.
 </div>

</body>
</html>

${this.title}

Code Editor : struct.html