<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>27.7. atexit — Exit handlers — Python v3.1.1 documentation</title>
<link rel="stylesheet" href="../_static/default.css" type="text/css" />
<link rel="stylesheet" href="../_static/pygments.css" type="text/css" />
<script type="text/javascript">
var DOCUMENTATION_OPTIONS = {
URL_ROOT: '../',
VERSION: '3.1.1',
COLLAPSE_MODINDEX: false,
FILE_SUFFIX: '.html',
HAS_SOURCE: true
};
</script>
<script type="text/javascript" src="../_static/jquery.js"></script>
<script type="text/javascript" src="../_static/doctools.js"></script>
<link rel="search" type="application/opensearchdescription+xml"
title="Search within Python v3.1.1 documentation"
href="../_static/opensearch.xml"/>
<link rel="author" title="About these documents" href="../about.html" />
<link rel="copyright" title="Copyright" href="../copyright.html" />
<link rel="top" title="Python v3.1.1 documentation" href="../index.html" />
<link rel="up" title="27. Python Runtime Services" href="python.html" />
<link rel="next" title="27.8. traceback — Print or retrieve a stack traceback" href="traceback.html" />
<link rel="prev" title="27.6. abc — Abstract Base Classes" href="abc.html" />
<link rel="shortcut icon" type="image/png" href="../_static/py.png" />
</head>
<body>
<div class="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="../modindex.html" title="Global Module Index"
accesskey="M">modules</a> |</li>
<li class="right" >
<a href="traceback.html" title="27.8. traceback — Print or retrieve a stack traceback"
accesskey="N">next</a> |</li>
<li class="right" >
<a href="abc.html" title="27.6. abc — Abstract Base Classes"
accesskey="P">previous</a> |</li>
<li><img src="../_static/py.png" alt=""
style="vertical-align: middle; margin-top: -1px"/></li>
<li><a href="../index.html">Python v3.1.1 documentation</a> »</li>
<li><a href="index.html" >The Python Standard Library</a> »</li>
<li><a href="python.html" accesskey="U">27. Python Runtime Services</a> »</li>
</ul>
</div>
<div class="document">
<div class="documentwrapper">
<div class="bodywrapper">
<div class="body">
<div class="section" id="module-atexit">
<h1>27.7. <tt class="xref docutils literal"><span class="pre">atexit</span></tt> — Exit handlers<a class="headerlink" href="#module-atexit" title="Permalink to this headline">¶</a></h1>
<p>The <tt class="xref docutils literal"><span class="pre">atexit</span></tt> module defines functions to register and unregister cleanup
functions. Functions thus registered are automatically executed upon normal
interpreter termination.</p>
<p>Note: the functions registered via this module are not called when the program
is killed by a signal, when a Python fatal internal error is detected, or when
<a title="os._exit" class="reference external" href="os.html#os._exit"><tt class="xref docutils literal"><span class="pre">os._exit()</span></tt></a> is called.</p>
<dl class="function">
<dt id="atexit.register">
<tt class="descclassname">atexit.</tt><tt class="descname">register</tt><big>(</big><em>func</em>, <em>*args</em>, <em>**kargs</em><big>)</big><a class="headerlink" href="#atexit.register" title="Permalink 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 title="atexit.register" class="reference internal" href="#atexit.register"><tt class="xref docutils literal"><span class="pre">register()</span></tt></a>.</p>
<p>At normal program termination (for instance, if <a title="sys.exit" class="reference external" href="sys.html#sys.exit"><tt class="xref docutils literal"><span class="pre">sys.exit()</span></tt></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 title="exceptions.SystemExit" class="reference external" href="exceptions.html#exceptions.SystemExit"><tt class="xref docutils literal"><span class="pre">SystemExit</span></tt></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
without binding the original name to <tt class="xref docutils literal"><span class="pre">None</span></tt>.</p>
</dd></dl>
<dl class="function">
<dt id="atexit.unregister">
<tt class="descclassname">atexit.</tt><tt class="descname">unregister</tt><big>(</big><em>func</em><big>)</big><a class="headerlink" href="#atexit.unregister" title="Permalink to this definition">¶</a></dt>
<dd>Remove a function <em>func</em> from the list of functions to be run at interpreter-
shutdown. After calling <a title="atexit.unregister" class="reference internal" href="#atexit.unregister"><tt class="xref docutils literal"><span class="pre">unregister()</span></tt></a>, <em>func</em> is guaranteed not to be
called when the interpreter shuts down.</dd></dl>
<div class="admonition-see-also admonition seealso">
<p class="first admonition-title">See also</p>
<dl class="last docutils">
<dt>Module <a title="(Unix) GNU readline support for Python." class="reference external" href="readline.html#module-readline"><tt class="xref docutils literal"><span class="pre">readline</span></tt></a></dt>
<dd>Useful example of <tt class="xref docutils literal"><span class="pre">atexit</span></tt> to read and write <a title="(Unix) GNU readline support for Python." class="reference external" href="readline.html#module-readline"><tt class="xref docutils literal"><span class="pre">readline</span></tt></a> history
files.</dd>
</dl>
</div>
<div class="section" id="atexit-example">
<span id="id1"></span><h2>27.7.1. <tt class="xref docutils literal"><span class="pre">atexit</span></tt> Example<a class="headerlink" href="#atexit-example" title="Permalink to this headline">¶</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"><pre>try:
_count = int(open("/tmp/counter").read())
except IOError:
_count = 0
def incrcounter(n):
global _count
_count = _count + n
def savecounter():
open("/tmp/counter", "w").write("%d" % _count)
import atexit
atexit.register(savecounter)</pre>
</div>
<p>Positional and keyword arguments may also be passed to <a title="atexit.register" class="reference internal" href="#atexit.register"><tt class="xref docutils literal"><span class="pre">register()</span></tt></a> to be
passed along to the registered function when it is called:</p>
<div class="highlight-python3"><div class="highlight"><pre><span class="k">def</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="s">'Goodbye, %s, it was %s to meet you.'</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="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="s">'Donny'</span><span class="p">,</span> <span class="s">'nice'</span><span class="p">)</span>
<span class="c"># 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="s">'nice'</span><span class="p">,</span> <span class="n">name</span><span class="o">=</span><span class="s">'Donny'</span><span class="p">)</span>
</pre></div>
</div>
<p>Usage as a <a class="reference external" href="../glossary.html#term-decorator"><em class="xref">decorator</em></a>:</p>
<div class="highlight-python3"><div class="highlight"><pre><span class="kn">import</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="nf">goodbye</span><span class="p">():</span>
<span class="nb">print</span><span class="p">(</span><span class="s">"You are now leaving the Python sector."</span><span class="p">)</span>
</pre></div>
</div>
<p>This obviously only works with functions that don’t take arguments.</p>
</div>
</div>
</div>
</div>
</div>
<div class="sphinxsidebar">
<div class="sphinxsidebarwrapper">
<h3><a href="../contents.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference external" href="">27.7. <tt class="docutils literal"><span class="pre">atexit</span></tt> — Exit handlers</a><ul>
<li><a class="reference external" href="#atexit-example">27.7.1. <tt class="docutils literal"><span class="pre">atexit</span></tt> Example</a></li>
</ul>
</li>
</ul>
<h4>Previous topic</h4>
<p class="topless"><a href="abc.html"
title="previous chapter">27.6. <tt class="docutils literal docutils literal"><span class="pre">abc</span></tt> — Abstract Base Classes</a></p>
<h4>Next topic</h4>
<p class="topless"><a href="traceback.html"
title="next chapter">27.8. <tt class="docutils literal docutils literal"><span class="pre">traceback</span></tt> — Print or retrieve a stack traceback</a></p>
<h3>This Page</h3>
<ul class="this-page-menu">
<li><a href="../_sources/library/atexit.txt"
rel="nofollow">Show Source</a></li>
</ul>
<div id="searchbox" style="display: none">
<h3>Quick search</h3>
<form class="search" action="../search.html" method="get">
<input type="text" name="q" size="18" />
<input type="submit" value="Go" />
<input type="hidden" name="check_keywords" value="yes" />
<input type="hidden" name="area" value="default" />
</form>
<p class="searchtip" style="font-size: 90%">
Enter search terms or a module, class or function name.
</p>
</div>
<script type="text/javascript">$('#searchbox').show(0);</script>
</div>
</div>
<div class="clearer"></div>
</div>
<div class="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="../modindex.html" title="Global Module Index"
>modules</a> |</li>
<li class="right" >
<a href="traceback.html" title="27.8. traceback — Print or retrieve a stack traceback"
>next</a> |</li>
<li class="right" >
<a href="abc.html" title="27.6. abc — Abstract Base Classes"
>previous</a> |</li>
<li><img src="../_static/py.png" alt=""
style="vertical-align: middle; margin-top: -1px"/></li>
<li><a href="../index.html">Python v3.1.1 documentation</a> »</li>
<li><a href="index.html" >The Python Standard Library</a> »</li>
<li><a href="python.html" >27. Python Runtime Services</a> »</li>
</ul>
</div>
<div class="footer">
© <a href="../copyright.html">Copyright</a> 1990-2009, Python Software Foundation.
<br />
The Python Software Foundation is a non-profit corporation.
<a href="http://www.python.org/psf/donations/">Please donate.</a>
<br />
Last updated on Aug 16, 2009.
Created using <a href="http://sphinx.pocoo.org/">Sphinx</a> 0.6.2.
</div>
</body>
</html>
distrib
>
Mandriva
>
2010.0
>
i586
>
media
>
contrib-release
>
by-pkgid
>
e870e6598e1c7e3918555a3d0ba5f3d4
>
files
>
570
