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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="Content-Type" content="text/html; charset=utf-8" /> <title>8.19. repr — Alternate repr() implementation — Python v2.6.6 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: '2.6.6', 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 v2.6.6 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 v2.6.6 documentation" href="../index.html" /> <link rel="up" title="8. 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Data Types</a> »</li> </ul> </div> <div class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body"> <div class="section" id="module-repr"> <h1>8.19. <tt class="xref docutils literal"><span class="pre">repr</span></tt> — Alternate <a title="repr" class="reference external" href="functions.html#repr"><tt class="xref docutils literal"><span class="pre">repr()</span></tt></a> implementation<a class="headerlink" href="#module-repr" title="Permalink to this headline">¶</a></h1> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">The <tt class="xref docutils literal"><span class="pre">repr</span></tt> module has been renamed to <tt class="xref docutils literal"><span class="pre">reprlib</span></tt> in Python 3.0. The <a class="reference external" href="../glossary.html#term-to3"><em class="xref">2to3</em></a> tool will automatically adapt imports when converting your sources to 3.0.</p> </div> <p>The <tt class="xref docutils literal"><span class="pre">repr</span></tt> module provides a means for producing object representations with limits on the size of the resulting strings. This is used in the Python debugger and may be useful in other contexts as well.</p> <p>This module provides a class, an instance, and a function:</p> <dl class="class"> <dt id="repr.Repr"> <em class="property">class </em><tt class="descclassname">repr.</tt><tt class="descname">Repr</tt><a class="headerlink" href="#repr.Repr" title="Permalink to this definition">¶</a></dt> <dd>Class which provides formatting services useful in implementing functions similar to the built-in <a title="repr" class="reference external" href="functions.html#repr"><tt class="xref docutils literal"><span class="pre">repr()</span></tt></a>; size limits for different object types are added to avoid the generation of representations which are excessively long.</dd></dl> <dl class="data"> <dt id="repr.aRepr"> <tt class="descclassname">repr.</tt><tt class="descname">aRepr</tt><a class="headerlink" href="#repr.aRepr" title="Permalink to this definition">¶</a></dt> <dd>This is an instance of <a title="repr.Repr" class="reference internal" href="#repr.Repr"><tt class="xref docutils literal"><span class="pre">Repr</span></tt></a> which is used to provide the <a title="repr.repr" class="reference internal" href="#repr.repr"><tt class="xref docutils literal"><span class="pre">repr()</span></tt></a> function described below. Changing the attributes of this object will affect the size limits used by <a title="repr.repr" class="reference internal" href="#repr.repr"><tt class="xref docutils literal"><span class="pre">repr()</span></tt></a> and the Python debugger.</dd></dl> <dl class="function"> <dt id="repr.repr"> <tt class="descclassname">repr.</tt><tt class="descname">repr</tt><big>(</big><em>obj</em><big>)</big><a class="headerlink" href="#repr.repr" title="Permalink to this definition">¶</a></dt> <dd>This is the <a title="repr.Repr.repr" class="reference internal" href="#repr.Repr.repr"><tt class="xref docutils literal"><span class="pre">repr()</span></tt></a> method of <tt class="docutils literal"><span class="pre">aRepr</span></tt>. It returns a string similar to that returned by the built-in function of the same name, but with limits on most sizes.</dd></dl> <div class="section" id="repr-objects"> <span id="id1"></span><h2>8.19.1. Repr Objects<a class="headerlink" href="#repr-objects" title="Permalink to this headline">¶</a></h2> <p><a title="repr.Repr" class="reference internal" href="#repr.Repr"><tt class="xref docutils literal"><span class="pre">Repr</span></tt></a> instances provide several members which can be used to provide size limits for the representations of different object types, and methods which format specific object types.</p> <dl class="attribute"> <dt id="repr.Repr.maxlevel"> <tt class="descclassname">Repr.</tt><tt class="descname">maxlevel</tt><a class="headerlink" href="#repr.Repr.maxlevel" title="Permalink to this definition">¶</a></dt> <dd>Depth limit on the creation of recursive representations. The default is <tt class="docutils literal"><span class="pre">6</span></tt>.</dd></dl> <dl class="attribute"> <dt id="repr.Repr.maxdict"> <tt class="descclassname">Repr.</tt><tt class="descname">maxdict</tt><a class="headerlink" href="#repr.Repr.maxdict" title="Permalink to this definition">¶</a></dt> <dt id="repr.Repr.maxlist"> <tt class="descclassname">Repr.</tt><tt class="descname">maxlist</tt><a class="headerlink" href="#repr.Repr.maxlist" title="Permalink to this definition">¶</a></dt> <dt id="repr.Repr.maxtuple"> <tt class="descclassname">Repr.</tt><tt class="descname">maxtuple</tt><a class="headerlink" href="#repr.Repr.maxtuple" title="Permalink to this definition">¶</a></dt> <dt id="repr.Repr.maxset"> <tt class="descclassname">Repr.</tt><tt class="descname">maxset</tt><a class="headerlink" href="#repr.Repr.maxset" title="Permalink to this definition">¶</a></dt> <dt id="repr.Repr.maxfrozenset"> <tt class="descclassname">Repr.</tt><tt class="descname">maxfrozenset</tt><a class="headerlink" href="#repr.Repr.maxfrozenset" title="Permalink to this definition">¶</a></dt> <dt id="repr.Repr.maxdeque"> <tt class="descclassname">Repr.</tt><tt class="descname">maxdeque</tt><a class="headerlink" href="#repr.Repr.maxdeque" title="Permalink to this definition">¶</a></dt> <dt id="repr.Repr.maxarray"> <tt class="descclassname">Repr.</tt><tt class="descname">maxarray</tt><a class="headerlink" href="#repr.Repr.maxarray" title="Permalink to this definition">¶</a></dt> <dd><p>Limits on the number of entries represented for the named object type. The default is <tt class="docutils literal"><span class="pre">4</span></tt> for <a title="repr.Repr.maxdict" class="reference internal" href="#repr.Repr.maxdict"><tt class="xref docutils literal"><span class="pre">maxdict</span></tt></a>, <tt class="docutils literal"><span class="pre">5</span></tt> for <a title="repr.Repr.maxarray" class="reference internal" href="#repr.Repr.maxarray"><tt class="xref docutils literal"><span class="pre">maxarray</span></tt></a>, and <tt class="docutils literal"><span class="pre">6</span></tt> for the others.</p> <p class="versionadded"> <span class="versionmodified">New in version 2.4: </span><a title="repr.Repr.maxset" class="reference internal" href="#repr.Repr.maxset"><tt class="xref docutils literal"><span class="pre">maxset</span></tt></a>, <a title="repr.Repr.maxfrozenset" class="reference internal" href="#repr.Repr.maxfrozenset"><tt class="xref docutils literal"><span class="pre">maxfrozenset</span></tt></a>, and <a title="set" class="reference external" href="stdtypes.html#set"><tt class="xref docutils literal"><span class="pre">set</span></tt></a>.</p> </dd></dl> <dl class="attribute"> <dt id="repr.Repr.maxlong"> <tt class="descclassname">Repr.</tt><tt class="descname">maxlong</tt><a class="headerlink" href="#repr.Repr.maxlong" title="Permalink to this definition">¶</a></dt> <dd>Maximum number of characters in the representation for a long integer. Digits are dropped from the middle. The default is <tt class="docutils literal"><span class="pre">40</span></tt>.</dd></dl> <dl class="attribute"> <dt id="repr.Repr.maxstring"> <tt class="descclassname">Repr.</tt><tt class="descname">maxstring</tt><a class="headerlink" href="#repr.Repr.maxstring" title="Permalink to this definition">¶</a></dt> <dd>Limit on the number of characters in the representation of the string. Note that the “normal” representation of the string is used as the character source: if escape sequences are needed in the representation, these may be mangled when the representation is shortened. The default is <tt class="docutils literal"><span class="pre">30</span></tt>.</dd></dl> <dl class="attribute"> <dt id="repr.Repr.maxother"> <tt class="descclassname">Repr.</tt><tt class="descname">maxother</tt><a class="headerlink" href="#repr.Repr.maxother" title="Permalink to this definition">¶</a></dt> <dd>This limit is used to control the size of object types for which no specific formatting method is available on the <a title="repr.Repr" class="reference internal" href="#repr.Repr"><tt class="xref docutils literal"><span class="pre">Repr</span></tt></a> object. It is applied in a similar manner as <a title="repr.Repr.maxstring" class="reference internal" href="#repr.Repr.maxstring"><tt class="xref docutils literal"><span class="pre">maxstring</span></tt></a>. The default is <tt class="docutils literal"><span class="pre">20</span></tt>.</dd></dl> <dl class="method"> <dt id="repr.Repr.repr"> <tt class="descclassname">Repr.</tt><tt class="descname">repr</tt><big>(</big><em>obj</em><big>)</big><a class="headerlink" href="#repr.Repr.repr" title="Permalink to this definition">¶</a></dt> <dd>The equivalent to the built-in <a title="repr" class="reference external" href="functions.html#repr"><tt class="xref docutils literal"><span class="pre">repr()</span></tt></a> that uses the formatting imposed by the instance.</dd></dl> <dl class="method"> <dt id="repr.Repr.repr1"> <tt class="descclassname">Repr.</tt><tt class="descname">repr1</tt><big>(</big><em>obj</em>, <em>level</em><big>)</big><a class="headerlink" href="#repr.Repr.repr1" title="Permalink to this definition">¶</a></dt> <dd>Recursive implementation used by <a title="repr.Repr.repr" class="reference internal" href="#repr.Repr.repr"><tt class="xref docutils literal"><span class="pre">repr()</span></tt></a>. This uses the type of <em>obj</em> to determine which formatting method to call, passing it <em>obj</em> and <em>level</em>. The type-specific methods should call <a title="repr.Repr.repr1" class="reference internal" href="#repr.Repr.repr1"><tt class="xref docutils literal"><span class="pre">repr1()</span></tt></a> to perform recursive formatting, with <tt class="docutils literal"><span class="pre">level</span> <span class="pre">-</span> <span class="pre">1</span></tt> for the value of <em>level</em> in the recursive call.</dd></dl> <dl class="method"> <dt> <tt class="descclassname">Repr.</tt><tt class="descname">repr_TYPE</tt><big>(</big><em>obj</em>, <em>level</em><big>)</big></dt> <dd>Formatting methods for specific types are implemented as methods with a name based on the type name. In the method name, <strong>TYPE</strong> is replaced by <tt class="docutils literal"><span class="pre">string.join(string.split(type(obj).__name__,</span> <span class="pre">'_'))</span></tt>. Dispatch to these methods is handled by <tt class="xref docutils literal"><span class="pre">repr1()</span></tt>. Type-specific methods which need to recursively format a value should call <tt class="docutils literal"><span class="pre">self.repr1(subobj,</span> <span class="pre">level</span> <span class="pre">-</span> <span class="pre">1)</span></tt>.</dd></dl> </div> <div class="section" id="subclassing-repr-objects"> <span id="subclassing-reprs"></span><h2>8.19.2. Subclassing Repr Objects<a class="headerlink" href="#subclassing-repr-objects" title="Permalink to this headline">¶</a></h2> <p>The use of dynamic dispatching by <a title="repr.Repr.repr1" class="reference internal" href="#repr.Repr.repr1"><tt class="xref docutils literal"><span class="pre">Repr.repr1()</span></tt></a> allows subclasses of <a title="repr.Repr" class="reference internal" href="#repr.Repr"><tt class="xref docutils literal"><span class="pre">Repr</span></tt></a> to add support for additional built-in object types or to modify the handling of types already supported. This example shows how special support for file objects could be added:</p> <div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">repr</span> <span class="kn">as</span> <span class="nn">reprlib</span> <span class="kn">import</span> <span class="nn">sys</span> <span class="k">class</span> <span class="nc">MyRepr</span><span class="p">(</span><span class="n">reprlib</span><span class="o">.</span><span class="n">Repr</span><span class="p">):</span> <span class="k">def</span> <span class="nf">repr_file</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">obj</span><span class="p">,</span> <span class="n">level</span><span class="p">):</span> <span class="k">if</span> <span class="n">obj</span><span class="o">.</span><span class="n">name</span> <span class="ow">in</span> <span class="p">[</span><span class="s">'<stdin>'</span><span class="p">,</span> <span class="s">'<stdout>'</span><span class="p">,</span> <span class="s">'<stderr>'</span><span class="p">]:</span> <span class="k">return</span> <span class="n">obj</span><span class="o">.</span><span class="n">name</span> <span class="k">else</span><span class="p">:</span> <span class="k">return</span> <span class="nb">repr</span><span class="p">(</span><span class="n">obj</span><span class="p">)</span> <span class="n">aRepr</span> <span class="o">=</span> <span class="n">MyRepr</span><span class="p">()</span> <span class="k">print</span> <span class="n">aRepr</span><span class="o">.</span><span class="n">repr</span><span class="p">(</span><span class="n">sys</span><span class="o">.</span><span class="n">stdin</span><span class="p">)</span> <span class="c"># prints '<stdin>'</span> </pre></div> </div> </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="#">8.19. <tt class="docutils literal"><span class="pre">repr</span></tt> — Alternate <tt class="docutils literal"><span class="pre">repr()</span></tt> implementation</a><ul> <li><a class="reference external" href="#repr-objects">8.19.1. Repr Objects</a></li> <li><a class="reference external" href="#subclassing-repr-objects">8.19.2. Subclassing Repr Objects</a></li> </ul> </li> </ul> <h4>Previous topic</h4> <p class="topless"><a href="pprint.html" title="previous chapter">8.18. <tt class="docutils literal docutils literal docutils literal"><span class="pre">pprint</span></tt> — Data pretty printer</a></p> <h4>Next topic</h4> <p class="topless"><a href="numeric.html" title="next chapter">9. 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