bunny-lab/Borealis
bunny-lab/Borealis
2
0
Fork 0
Code Issues 10 Pull Requests Actions Packages Projects 1 Releases Wiki Activity
Borealis/Dependencies/Python/Doc/html/library/atexit.html

447 lines
27 KiB
HTML
Raw Blame History

This file contains ambiguous Unicode characters

This file contains Unicode characters that might be confused with other characters. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

<!DOCTYPE html>
<html lang="en" data-content_root="../">
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" /><meta name="viewport" content="width=device-width, initial-scale=1" />
<meta property="og:title" content="atexit — Exit handlers" />
<meta property="og:type" content="website" />
<meta property="og:url" content="https://docs.python.org/3/library/atexit.html" />
<meta property="og:site_name" content="Python documentation" />
<meta property="og:description" content="The atexit module defines functions to register and unregister cleanup functions. Functions thus registered are automatically executed upon normal interpreter termination. atexit runs these functio..." />
<meta property="og:image" content="https://docs.python.org/3/_static/og-image.png" />
<meta property="og:image:alt" content="Python documentation" />
<meta name="description" content="The atexit module defines functions to register and unregister cleanup functions. Functions thus registered are automatically executed upon normal interpreter termination. atexit runs these functio..." />
<meta property="og:image:width" content="200">
<meta property="og:image:height" content="200">
<meta name="theme-color" content="#3776ab">
<title>atexit — Exit handlers &#8212; Python 3.13.3 documentation</title><meta name="viewport" content="width=device-width, initial-scale=1.0">
<link rel="stylesheet" type="text/css" href="../_static/pygments.css?v=b86133f3" />
<link rel="stylesheet" type="text/css" href="../_static/pydoctheme.css?v=23252803" />
<link id="pygments_dark_css" media="(prefers-color-scheme: dark)" rel="stylesheet" type="text/css" href="../_static/pygments_dark.css?v=5349f25f" />
<script src="../_static/documentation_options.js?v=5d57ca2d"></script>
<script src="../_static/doctools.js?v=9bcbadda"></script>
<script src="../_static/sphinx_highlight.js?v=dc90522c"></script>
<script src="../_static/sidebar.js"></script>
<link rel="search" type="application/opensearchdescription+xml"
title="Search within Python 3.13.3 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="traceback — Print or retrieve a stack traceback" href="traceback.html" />
<link rel="prev" title="abc — Abstract Base Classes" href="abc.html" />
<link rel="canonical" href="https://docs.python.org/3/library/atexit.html">
<style>
@media only screen {
table.full-width-table {
width: 100%;
}
}
</style>
<link rel="stylesheet" href="../_static/pydoctheme_dark.css" media="(prefers-color-scheme: dark)" id="pydoctheme_dark_css">
<link rel="shortcut icon" type="image/png" href="../_static/py.svg" />
<script type="text/javascript" src="../_static/copybutton.js"></script>
<script type="text/javascript" src="../_static/menu.js"></script>
<script type="text/javascript" src="../_static/search-focus.js"></script>
<script type="text/javascript" src="../_static/themetoggle.js"></script>
<script type="text/javascript" src="../_static/rtd_switcher.js"></script>
<meta name="readthedocs-addons-api-version" content="1">
</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" />
<nav class="nav-content" role="navigation">
<label for="menuToggler" class="toggler__label">
<span></span>
</label>
<span class="nav-items-wrapper">
<a href="https://www.python.org/" class="nav-logo">
<img src="../_static/py.svg" alt="Python logo"/>
</a>
<span class="version_switcher_placeholder"></span>
<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" fill="currentColor" 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"></path>
</svg>
<input placeholder="Quick search" aria-label="Quick search" type="search" name="q" />
<input type="submit" value="Go"/>
</form>
</span>
</nav>
<div class="menu-wrapper">
<nav class="menu" role="navigation" aria-label="main navigation">
<div class="language_switcher_placeholder"></div>
<label class="theme-selector-label">
Theme
<select class="theme-selector" oninput="activateTheme(this.value)">
<option value="auto" selected>Auto</option>
<option value="light">Light</option>
<option value="dark">Dark</option>
</select>
</label>
<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"><span class="pre">atexit</span></code> — Exit handlers</a><ul>
<li><a class="reference internal" href="#atexit-example"><code class="xref py py-mod docutils literal notranslate"><span class="pre">atexit</span></code> Example</a></li>
</ul>
</li>
</ul>
</div>
<div>
<h4>Previous topic</h4>
<p class="topless"><a href="abc.html"
title="previous chapter"><code class="xref py py-mod docutils literal notranslate"><span class="pre">abc</span></code> — Abstract Base Classes</a></p>
</div>
<div>
<h4>Next topic</h4>
<p class="topless"><a href="traceback.html"
title="next chapter"><code class="xref py py-mod docutils literal notranslate"><span class="pre">traceback</span></code> — Print or retrieve a stack traceback</a></p>
</div>
<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/main/Doc/library/atexit.rst"
rel="nofollow">Show Source
</a>
</li>
</ul>
</div>
</nav>
</div>
</div>
<div class="related" role="navigation" aria-label="Related">
<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="traceback.html" title="traceback — Print or retrieve a stack traceback"
accesskey="N">next</a> |</li>
<li class="right" >
<a href="abc.html" title="abc — Abstract Base Classes"
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">3.13.3 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="python.html" accesskey="U">Python Runtime Services</a> &#187;</li>
<li class="nav-item nav-item-this"><a href=""><code class="xref py py-mod docutils literal notranslate"><span class="pre">atexit</span></code> — Exit handlers</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="search" name="q" id="search-box" />
<input type="submit" value="Go" />
</form>
</div>
|
</li>
<li class="right">
<label class="theme-selector-label">
Theme
<select class="theme-selector" oninput="activateTheme(this.value)">
<option value="auto" selected>Auto</option>
<option value="light">Light</option>
<option value="dark">Dark</option>
</select>
</label> |</li>
</ul>
</div>
<div class="document">
<div class="documentwrapper">
<div class="bodywrapper">
<div class="body" role="main">
<section id="module-atexit">
<span id="atexit-exit-handlers"></span><h1><code class="xref py py-mod docutils literal notranslate"><span class="pre">atexit</span></code> — Exit handlers<a class="headerlink" href="#module-atexit" title="Link to this heading"></a></h1>
<hr class="docutils" />
<p>The <a class="reference internal" href="#module-atexit" title="atexit: Register and execute cleanup functions."><code class="xref py py-mod docutils literal notranslate"><span class="pre">atexit</span></code></a> module defines functions to register and unregister cleanup
functions. Functions thus registered are automatically executed upon normal
interpreter termination. <a class="reference internal" href="#module-atexit" title="atexit: Register and execute cleanup functions."><code class="xref py py-mod docutils literal notranslate"><span class="pre">atexit</span></code></a> runs these functions in the <em>reverse</em>
order in which they were registered; if you register <code class="docutils literal notranslate"><span class="pre">A</span></code>, <code class="docutils literal notranslate"><span class="pre">B</span></code>, and <code class="docutils literal notranslate"><span class="pre">C</span></code>,
at interpreter termination time they will be run in the order <code class="docutils literal notranslate"><span class="pre">C</span></code>, <code class="docutils literal notranslate"><span class="pre">B</span></code>,
<code class="docutils literal notranslate"><span class="pre">A</span></code>.</p>
<p><strong>Note:</strong> The functions registered via this module are not called when the
program is killed by a signal not handled by Python, when a Python fatal
internal error is detected, or when <a class="reference internal" href="os.html#os._exit" title="os._exit"><code class="xref py py-func docutils literal notranslate"><span class="pre">os._exit()</span></code></a> is called.</p>
<p><strong>Note:</strong> The effect of registering or unregistering functions from within
a cleanup function is undefined.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.7: </span>When used with C-API subinterpreters, registered functions
are local to the interpreter they were registered in.</p>
</div>
<dl class="py function">
<dt class="sig sig-object py" id="atexit.register">
<span class="sig-prename descclassname"><span class="pre">atexit.</span></span><span class="sig-name descname"><span class="pre">register</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">func</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">*</span></span><span class="n"><span class="pre">args</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">**</span></span><span class="n"><span class="pre">kwargs</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#atexit.register" title="Link to this definition"></a></dt>
<dd><p>Register <em>func</em> as a function to be executed at termination. Any optional
arguments that are to be passed to <em>func</em> must be passed as arguments to
<a class="reference internal" href="#atexit.register" title="atexit.register"><code class="xref py py-func docutils literal notranslate"><span class="pre">register()</span></code></a>. It is possible to register the same function and arguments
more than once.</p>
<p>At normal program termination (for instance, if <a class="reference internal" href="sys.html#sys.exit" title="sys.exit"><code class="xref py py-func docutils literal notranslate"><span class="pre">sys.exit()</span></code></a> is called or
the main module’s execution completes), all functions registered are called in
last in, first out order. The assumption is that lower level modules will
normally be imported before higher level modules and thus must be cleaned up
later.</p>
<p>If an exception is raised during execution of the exit handlers, a traceback is
printed (unless <a class="reference internal" href="exceptions.html#SystemExit" title="SystemExit"><code class="xref py py-exc docutils literal notranslate"><span class="pre">SystemExit</span></code></a> is raised) and the exception information is
saved. After all exit handlers have had a chance to run, the last exception to
be raised is re-raised.</p>
<p>This function returns <em>func</em>, which makes it possible to use it as a
decorator.</p>
<div class="admonition warning">
<p class="admonition-title">Warning</p>
<p>Starting new threads or calling <a class="reference internal" href="os.html#os.fork" title="os.fork"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.fork()</span></code></a> from a registered
function can lead to race condition between the main Python
runtime thread freeing thread states while internal <a class="reference internal" href="threading.html#module-threading" title="threading: Thread-based parallelism."><code class="xref py py-mod docutils literal notranslate"><span class="pre">threading</span></code></a>
routines or the new process try to use that state. This can lead to
crashes rather than clean shutdown.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.12: </span>Attempts to start a new thread or <a class="reference internal" href="os.html#os.fork" title="os.fork"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.fork()</span></code></a> a new process
in a registered function now leads to <a class="reference internal" href="exceptions.html#RuntimeError" title="RuntimeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">RuntimeError</span></code></a>.</p>
</div>
</dd></dl>
<dl class="py function">
<dt class="sig sig-object py" id="atexit.unregister">
<span class="sig-prename descclassname"><span class="pre">atexit.</span></span><span class="sig-name descname"><span class="pre">unregister</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">func</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#atexit.unregister" title="Link to this definition"></a></dt>
<dd><p>Remove <em>func</em> from the list of functions to be run at interpreter shutdown.
<a class="reference internal" href="#atexit.unregister" title="atexit.unregister"><code class="xref py py-func docutils literal notranslate"><span class="pre">unregister()</span></code></a> silently does nothing if <em>func</em> was not previously
registered. If <em>func</em> has been registered more than once, every occurrence
of that function in the <a class="reference internal" href="#module-atexit" title="atexit: Register and execute cleanup functions."><code class="xref py py-mod docutils literal notranslate"><span class="pre">atexit</span></code></a> call stack will be removed. Equality
comparisons (<code class="docutils literal notranslate"><span class="pre">==</span></code>) are used internally during unregistration, so function
references do not need to have matching identities.</p>
</dd></dl>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<dl class="simple">
<dt>Module <a class="reference internal" href="readline.html#module-readline" title="readline: GNU readline support for Python. (Unix)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">readline</span></code></a></dt><dd><p>Useful example of <a class="reference internal" href="#module-atexit" title="atexit: Register and execute cleanup functions."><code class="xref py py-mod docutils literal notranslate"><span class="pre">atexit</span></code></a> to read and write <a class="reference internal" href="readline.html#module-readline" title="readline: GNU readline support for Python. (Unix)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">readline</span></code></a> history
files.</p>
</dd>
</dl>
</div>
<section id="atexit-example">
<span id="id1"></span><h2><a class="reference internal" href="#module-atexit" title="atexit: Register and execute cleanup functions."><code class="xref py py-mod docutils literal notranslate"><span class="pre">atexit</span></code></a> Example<a class="headerlink" href="#atexit-example" title="Link to this heading"></a></h2>
<p>The following simple example demonstrates how a module can initialize a counter
from a file when it is imported and save the counter’s updated value
automatically when the program terminates without relying on the application
making an explicit call into this module at termination.</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">try</span><span class="p">:</span>
<span class="k">with</span> <span class="nb">open</span><span class="p">(</span><span class="s1">&#39;counterfile&#39;</span><span class="p">)</span> <span class="k">as</span> <span class="n">infile</span><span class="p">:</span>
<span class="n">_count</span> <span class="o">=</span> <span class="nb">int</span><span class="p">(</span><span class="n">infile</span><span class="o">.</span><span class="n">read</span><span class="p">())</span>
<span class="k">except</span> <span class="ne">FileNotFoundError</span><span class="p">:</span>
<span class="n">_count</span> <span class="o">=</span> <span class="mi">0</span>
<span class="k">def</span><span class="w"> </span><span class="nf">incrcounter</span><span class="p">(</span><span class="n">n</span><span class="p">):</span>
<span class="k">global</span> <span class="n">_count</span>
<span class="n">_count</span> <span class="o">=</span> <span class="n">_count</span> <span class="o">+</span> <span class="n">n</span>
<span class="k">def</span><span class="w"> </span><span class="nf">savecounter</span><span class="p">():</span>
<span class="k">with</span> <span class="nb">open</span><span class="p">(</span><span class="s1">&#39;counterfile&#39;</span><span class="p">,</span> <span class="s1">&#39;w&#39;</span><span class="p">)</span> <span class="k">as</span> <span class="n">outfile</span><span class="p">:</span>
<span class="n">outfile</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s1">&#39;</span><span class="si">%d</span><span class="s1">&#39;</span> <span class="o">%</span> <span class="n">_count</span><span class="p">)</span>
<span class="kn">import</span><span class="w"> </span><span class="nn">atexit</span>
<span class="n">atexit</span><span class="o">.</span><span class="n">register</span><span class="p">(</span><span class="n">savecounter</span><span class="p">)</span>
</pre></div>
</div>
<p>Positional and keyword arguments may also be passed to <a class="reference internal" href="#atexit.register" title="atexit.register"><code class="xref py py-func docutils literal notranslate"><span class="pre">register()</span></code></a> to be
passed along to the registered function when it is called:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">def</span><span class="w"> </span><span class="nf">goodbye</span><span class="p">(</span><span class="n">name</span><span class="p">,</span> <span class="n">adjective</span><span class="p">):</span>
<span class="nb">print</span><span class="p">(</span><span class="s1">&#39;Goodbye </span><span class="si">%s</span><span class="s1">, it was </span><span class="si">%s</span><span class="s1"> to meet you.&#39;</span> <span class="o">%</span> <span class="p">(</span><span class="n">name</span><span class="p">,</span> <span class="n">adjective</span><span class="p">))</span>
<span class="kn">import</span><span class="w"> </span><span class="nn">atexit</span>
<span class="n">atexit</span><span class="o">.</span><span class="n">register</span><span class="p">(</span><span class="n">goodbye</span><span class="p">,</span> <span class="s1">&#39;Donny&#39;</span><span class="p">,</span> <span class="s1">&#39;nice&#39;</span><span class="p">)</span>
<span class="c1"># or:</span>
<span class="n">atexit</span><span class="o">.</span><span class="n">register</span><span class="p">(</span><span class="n">goodbye</span><span class="p">,</span> <span class="n">adjective</span><span class="o">=</span><span class="s1">&#39;nice&#39;</span><span class="p">,</span> <span class="n">name</span><span class="o">=</span><span class="s1">&#39;Donny&#39;</span><span class="p">)</span>
</pre></div>
</div>
<p>Usage as a <a class="reference internal" href="../glossary.html#term-decorator"><span class="xref std std-term">decorator</span></a>:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span><span class="w"> </span><span class="nn">atexit</span>
<span class="nd">@atexit</span><span class="o">.</span><span class="n">register</span>
<span class="k">def</span><span class="w"> </span><span class="nf">goodbye</span><span class="p">():</span>
<span class="nb">print</span><span class="p">(</span><span class="s1">&#39;You are now leaving the Python sector.&#39;</span><span class="p">)</span>
</pre></div>
</div>
<p>This only works with functions that can be called without arguments.</p>
</section>
</section>
<div class="clearer"></div>
</div>
</div>
</div>
<div class="sphinxsidebar" role="navigation" aria-label="Main">
<div class="sphinxsidebarwrapper">
<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"><span class="pre">atexit</span></code> — Exit handlers</a><ul>
<li><a class="reference internal" href="#atexit-example"><code class="xref py py-mod docutils literal notranslate"><span class="pre">atexit</span></code> Example</a></li>
</ul>
</li>
</ul>
</div>
<div>
<h4>Previous topic</h4>
<p class="topless"><a href="abc.html"
title="previous chapter"><code class="xref py py-mod docutils literal notranslate"><span class="pre">abc</span></code> — Abstract Base Classes</a></p>
</div>
<div>
<h4>Next topic</h4>
<p class="topless"><a href="traceback.html"
title="next chapter"><code class="xref py py-mod docutils literal notranslate"><span class="pre">traceback</span></code> — Print or retrieve a stack traceback</a></p>
</div>
<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/main/Doc/library/atexit.rst"
rel="nofollow">Show Source
</a>
</li>
</ul>
</div>
</div>
<div id="sidebarbutton" title="Collapse sidebar">
<span>«</span>
</div>
</div>
<div class="clearer"></div>
</div>
<div class="related" role="navigation" aria-label="Related">
<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="traceback.html" title="traceback — Print or retrieve a stack traceback"
>next</a> |</li>
<li class="right" >
<a href="abc.html" title="abc — Abstract Base Classes"
>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">3.13.3 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="python.html" >Python Runtime Services</a> &#187;</li>
<li class="nav-item nav-item-this"><a href=""><code class="xref py py-mod docutils literal notranslate"><span class="pre">atexit</span></code> — Exit handlers</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="search" name="q" id="search-box" />
<input type="submit" value="Go" />
</form>
</div>
|
</li>
<li class="right">
<label class="theme-selector-label">
Theme
<select class="theme-selector" oninput="activateTheme(this.value)">
<option value="auto" selected>Auto</option>
<option value="light">Light</option>
<option value="dark">Dark</option>
</select>
</label> |</li>
</ul>
</div>
<div class="footer">
&copy;
<a href="../copyright.html">
Copyright
</a>
2001-2025, Python Software Foundation.
<br />
This page is licensed under the Python Software Foundation License Version 2.
<br />
Examples, recipes, and other code in the documentation are additionally licensed under the Zero Clause BSD License.
<br />
See <a href="/license.html">History and License</a> for more information.<br />
<br />
The Python Software Foundation is a non-profit corporation.
<a href="https://www.python.org/psf/donations/">Please donate.</a>
<br />
<br />
Last updated on Apr 08, 2025 (14:33 UTC).
<a href="/bugs.html">Found a bug</a>?
<br />
Created using <a href="https://www.sphinx-doc.org/">Sphinx</a> 8.2.3.
</div>
</body>
</html>
Reference in New Issue View Git Blame Copy Permalink