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<!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="X-UA-Compatible" content="IE=Edge" /> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>11.3. copy_reg — Register pickle support functions — Python 2.7.18 documentation</title> <link rel="stylesheet" href="../_static/classic.css" type="text/css" /> <link rel="stylesheet" href="../_static/pygments.css" type="text/css" /> <script type="text/javascript" id="documentation_options" data-url_root="../" src="../_static/documentation_options.js"></script> <script type="text/javascript" src="../_static/jquery.js"></script> <script type="text/javascript" src="../_static/underscore.js"></script> <script type="text/javascript" src="../_static/doctools.js"></script> <script type="text/javascript" src="../_static/language_data.js"></script> <script type="text/javascript" src="../_static/sidebar.js"></script> <link rel="search" type="application/opensearchdescription+xml" title="Search within Python 2.7.18 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="11.4. shelve — Python object persistence" href="shelve.html" /> <link rel="prev" title="11.1. pickle — Python object serialization" href="pickle.html" /> <link rel="shortcut icon" type="image/png" href="../_static/py.png" /> <link rel="canonical" href="file:///usr/share/doc/python2.7/html/library/copy_reg.html" /> <script type="text/javascript" src="../_static/copybutton.js"></script> </head><body> <div id="outdated-warning" style="padding: .5em; text-align: center; background-color: #FFBABA; color: #6A0E0E;"> This document is for an old version of Python that is <a href="https://devguide.python.org/devcycle/#end-of-life-branches">no longer supported</a>. You should install the python3 and python3-doc packages and read the <a href="file:///usr/share/doc/python3-doc/html/library/copy_reg.html"> Python documentation for the Python3 version packaged in this release</a>. </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" 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="shelve.html" title="11.4. shelve — Python object persistence" accesskey="N">next</a> |</li> <li class="right" > <a href="pickle.html" title="11.1. pickle — Python object serialization" accesskey="P">previous</a> |</li> <li><img src="../_static/py.png" alt="" style="vertical-align: middle; margin-top: -1px"/></li> <li><a href="https://www.python.org/">Python</a> »</li> <li> <a href="../index.html">Python 2.7.18 documentation</a> » </li> <li class="nav-item nav-item-1"><a href="index.html" >The Python Standard Library</a> »</li> <li class="nav-item nav-item-2"><a href="persistence.html" accesskey="U">11. Data Persistence</a> »</li> </ul> </div> <div class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body" role="main"> <div class="section" id="module-copy_reg"> <span id="copy-reg-register-pickle-support-functions"></span><h1>11.3. <a class="reference internal" href="#module-copy_reg" title="copy_reg: Register pickle support functions."><code class="xref py py-mod docutils literal notranslate"><span class="pre">copy_reg</span></code></a> — Register <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"><span class="pre">pickle</span></code></a> support functions<a class="headerlink" href="#module-copy_reg" title="Permalink to this headline">¶</a></h1> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">The <a class="reference internal" href="#module-copy_reg" title="copy_reg: Register pickle support functions."><code class="xref py py-mod docutils literal notranslate"><span class="pre">copy_reg</span></code></a> module has been renamed to <code class="xref py py-mod docutils literal notranslate"><span class="pre">copyreg</span></code> in Python 3. The <a class="reference internal" href="../glossary.html#term-2to3"><span class="xref std std-term">2to3</span></a> tool will automatically adapt imports when converting your sources to Python 3.</p> </div> <p id="index-0">The <a class="reference internal" href="#module-copy_reg" title="copy_reg: Register pickle support functions."><code class="xref py py-mod docutils literal notranslate"><span class="pre">copy_reg</span></code></a> module offers a way to define functions used while pickling specific objects. The <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"><span class="pre">pickle</span></code></a>, <a class="reference internal" href="pickle.html#module-cPickle" title="cPickle: Faster version of pickle, but not subclassable."><code class="xref py py-mod docutils literal notranslate"><span class="pre">cPickle</span></code></a>, and <a class="reference internal" href="copy.html#module-copy" title="copy: Shallow and deep copy operations."><code class="xref py py-mod docutils literal notranslate"><span class="pre">copy</span></code></a> modules use those functions when pickling/copying those objects. The module provides configuration information about object constructors which are not classes. Such constructors may be factory functions or class instances.</p> <dl class="function"> <dt id="copy_reg.constructor"> <code class="descclassname">copy_reg.</code><code class="descname">constructor</code><span class="sig-paren">(</span><em>object</em><span class="sig-paren">)</span><a class="headerlink" href="#copy_reg.constructor" title="Permalink to this definition">¶</a></dt> <dd><p>Declares <em>object</em> to be a valid constructor. If <em>object</em> is not callable (and hence not valid as a constructor), raises <a class="reference internal" href="exceptions.html#exceptions.TypeError" title="exceptions.TypeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code></a>.</p> </dd></dl> <dl class="function"> <dt id="copy_reg.pickle"> <code class="descclassname">copy_reg.</code><code class="descname">pickle</code><span class="sig-paren">(</span><em>type</em>, <em>function</em><span class="optional">[</span>, <em>constructor</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#copy_reg.pickle" title="Permalink to this definition">¶</a></dt> <dd><p>Declares that <em>function</em> should be used as a “reduction” function for objects of type <em>type</em>; <em>type</em> must not be a “classic” class object. (Classic classes are handled differently; see the documentation for the <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"><span class="pre">pickle</span></code></a> module for details.) <em>function</em> should return either a string or a tuple containing two or three elements.</p> <p>The optional <em>constructor</em> parameter, if provided, is a callable object which can be used to reconstruct the object when called with the tuple of arguments returned by <em>function</em> at pickling time. <a class="reference internal" href="exceptions.html#exceptions.TypeError" title="exceptions.TypeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code></a> will be raised if <em>object</em> is a class or <em>constructor</em> is not callable.</p> <p>See the <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"><span class="pre">pickle</span></code></a> module for more details on the interface expected of <em>function</em> and <em>constructor</em>.</p> </dd></dl> <div class="section" id="example"> <h2>11.3.1. Example<a class="headerlink" href="#example" title="Permalink to this headline">¶</a></h2> <p>The example below would like to show how to register a pickle function and how it will be used:</p> <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">copy_reg</span><span class="o">,</span> <span class="nn">copy</span><span class="o">,</span> <span class="nn">pickle</span> <span class="gp">>>> </span><span class="k">class</span> <span class="nc">C</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span> <span class="gp">... </span> <span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">a</span><span class="p">):</span> <span class="gp">... </span> <span class="bp">self</span><span class="o">.</span><span class="n">a</span> <span class="o">=</span> <span class="n">a</span> <span class="gp">...</span> <span class="gp">>>> </span><span class="k">def</span> <span class="nf">pickle_c</span><span class="p">(</span><span class="n">c</span><span class="p">):</span> <span class="gp">... </span> <span class="nb">print</span><span class="p">(</span><span class="s2">"pickling a C instance..."</span><span class="p">)</span> <span class="gp">... </span> <span class="k">return</span> <span class="n">C</span><span class="p">,</span> <span class="p">(</span><span class="n">c</span><span class="o">.</span><span class="n">a</span><span class="p">,)</span> <span class="gp">...</span> <span class="gp">>>> </span><span class="n">copy_reg</span><span class="o">.</span><span class="n">pickle</span><span class="p">(</span><span class="n">C</span><span class="p">,</span> <span class="n">pickle_c</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">c</span> <span class="o">=</span> <span class="n">C</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">d</span> <span class="o">=</span> <span class="n">copy</span><span class="o">.</span><span class="n">copy</span><span class="p">(</span><span class="n">c</span><span class="p">)</span> <span class="go">pickling a C instance...</span> <span class="gp">>>> </span><span class="n">p</span> <span class="o">=</span> <span class="n">pickle</span><span class="o">.</span><span class="n">dumps</span><span class="p">(</span><span class="n">c</span><span class="p">)</span> <span class="go">pickling a C instance...</span> </pre></div> </div> </div> </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="#">11.3. <code class="docutils literal notranslate"><span class="pre">copy_reg</span></code> — Register <code class="docutils literal notranslate"><span class="pre">pickle</span></code> support functions</a><ul> <li><a class="reference internal" href="#example">11.3.1. Example</a></li> </ul> </li> </ul> <h4>Previous topic</h4> <p class="topless"><a href="pickle.html" title="previous chapter">11.1. <code class="docutils literal notranslate"><span class="pre">pickle</span></code> — Python object serialization</a></p> <h4>Next topic</h4> <p class="topless"><a href="shelve.html" title="next chapter">11.4. <code class="docutils literal notranslate"><span class="pre">shelve</span></code> — Python object persistence</a></p> <div role="note" aria-label="source link"> <h3>This Page</h3> <ul class="this-page-menu"> <li><a href="../_sources/library/copy_reg.rst.txt" rel="nofollow">Show Source</a></li> </ul> </div> <div id="searchbox" style="display: none" role="search"> <h3>Quick search</h3> <div class="searchformwrapper"> <form class="search" action="../search.html" method="get"> <input 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> </div> <script type="text/javascript">$('#searchbox').show(0);</script> </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="shelve.html" title="11.4. shelve — Python object persistence" >next</a> |</li> <li class="right" > <a href="pickle.html" title="11.1. pickle — Python object serialization" >previous</a> |</li> <li><img src="../_static/py.png" alt="" style="vertical-align: middle; margin-top: -1px"/></li> <li><a href="https://www.python.org/">Python</a> »</li> <li> <a href="../index.html">Python 2.7.18 documentation</a> » </li> <li class="nav-item nav-item-1"><a href="index.html" >The Python Standard Library</a> »</li> <li class="nav-item nav-item-2"><a href="persistence.html" >11. 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