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<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="admonition-title">Note</p>
<p>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>
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<ul>
<li><a class="reference internal" href="#">11.3. <code class="xref py py-mod docutils literal notranslate"><span class="pre">copy_reg</span></code> — Register <code class="xref py py-mod 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>
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<h4>Previous topic</h4>
<p class="topless"><a href="pickle.html"
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