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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>7.5. StringIO — Read and write strings as files — 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="7.7. textwrap — Text wrapping and filling" href="textwrap.html" /> <link rel="prev" title="7.4. difflib — Helpers for computing deltas" href="difflib.html" /> <link rel="shortcut icon" type="image/png" href="../_static/py.png" /> <link rel="canonical" href="file:///usr/share/doc/python2.7/html/library/stringio.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div id="outdated-warning" style="padding: .5em; text-align: center; background-color: #FFBABA; color: #6A0E0E;"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/stringio.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="textwrap.html" title="7.7. textwrap — Text wrapping and filling" accesskey="N">next</a> |</li> <li class="right" > <a href="difflib.html" title="7.4. difflib — Helpers for computing deltas" 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="strings.html" accesskey="U">7. String Services</a> »</li> </ul> </div> <div class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body" role="main"> <div class="section" id="module-StringIO"> <span id="stringio-read-and-write-strings-as-files"></span><h1>7.5. <a class="reference internal" href="#module-StringIO" title="StringIO: Read and write strings as if they were files."><code class="xref py py-mod docutils literal notranslate"><span class="pre">StringIO</span></code></a> — Read and write strings as files<a class="headerlink" href="#module-StringIO" title="Permalink to this headline">¶</a></h1> <p>This module implements a file-like class, <a class="reference internal" href="#StringIO.StringIO" title="StringIO.StringIO"><code class="xref py py-class docutils literal notranslate"><span class="pre">StringIO</span></code></a>, that reads and writes a string buffer (also known as <em>memory files</em>). See the description of file objects for operations (section <a class="reference internal" href="stdtypes.html#bltin-file-objects"><span class="std std-ref">File Objects</span></a>). (For standard strings, see <a class="reference internal" href="functions.html#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a> and <a class="reference internal" href="functions.html#unicode" title="unicode"><code class="xref py py-class docutils literal notranslate"><span class="pre">unicode</span></code></a>.)</p> <dl class="class"> <dt id="StringIO.StringIO"> <em class="property">class </em><code class="descclassname">StringIO.</code><code class="descname">StringIO</code><span class="sig-paren">(</span><span class="optional">[</span><em>buffer</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#StringIO.StringIO" title="Permalink to this definition">¶</a></dt> <dd><p>When a <a class="reference internal" href="#StringIO.StringIO" title="StringIO.StringIO"><code class="xref py py-class docutils literal notranslate"><span class="pre">StringIO</span></code></a> object is created, it can be initialized to an existing string by passing the string to the constructor. If no string is given, the <a class="reference internal" href="#StringIO.StringIO" title="StringIO.StringIO"><code class="xref py py-class docutils literal notranslate"><span class="pre">StringIO</span></code></a> will start empty. In both cases, the initial file position starts at zero.</p> <p>The <a class="reference internal" href="#StringIO.StringIO" title="StringIO.StringIO"><code class="xref py py-class docutils literal notranslate"><span class="pre">StringIO</span></code></a> object can accept either Unicode or 8-bit strings, but mixing the two may take some care. If both are used, 8-bit strings that cannot be interpreted as 7-bit ASCII (that use the 8th bit) will cause a <a class="reference internal" href="exceptions.html#exceptions.UnicodeError" title="exceptions.UnicodeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">UnicodeError</span></code></a> to be raised when <a class="reference internal" href="#StringIO.StringIO.getvalue" title="StringIO.StringIO.getvalue"><code class="xref py py-meth docutils literal notranslate"><span class="pre">getvalue()</span></code></a> is called.</p> </dd></dl> <p>The following methods of <a class="reference internal" href="#StringIO.StringIO" title="StringIO.StringIO"><code class="xref py py-class docutils literal notranslate"><span class="pre">StringIO</span></code></a> objects require special mention:</p> <dl class="method"> <dt id="StringIO.StringIO.getvalue"> <code class="descclassname">StringIO.</code><code class="descname">getvalue</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#StringIO.StringIO.getvalue" title="Permalink to this definition">¶</a></dt> <dd><p>Retrieve the entire contents of the “file” at any time before the <a class="reference internal" href="#StringIO.StringIO" title="StringIO.StringIO"><code class="xref py py-class docutils literal notranslate"><span class="pre">StringIO</span></code></a> object’s <a class="reference internal" href="#StringIO.StringIO.close" title="StringIO.StringIO.close"><code class="xref py py-meth docutils literal notranslate"><span class="pre">close()</span></code></a> method is called. See the note above for information about mixing Unicode and 8-bit strings; such mixing can cause this method to raise <a class="reference internal" href="exceptions.html#exceptions.UnicodeError" title="exceptions.UnicodeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">UnicodeError</span></code></a>.</p> </dd></dl> <dl class="method"> <dt id="StringIO.StringIO.close"> <code class="descclassname">StringIO.</code><code class="descname">close</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#StringIO.StringIO.close" title="Permalink to this definition">¶</a></dt> <dd><p>Free the memory buffer. Attempting to do further operations with a closed <a class="reference internal" href="#StringIO.StringIO" title="StringIO.StringIO"><code class="xref py py-class docutils literal notranslate"><span class="pre">StringIO</span></code></a> object will raise a <a class="reference internal" href="exceptions.html#exceptions.ValueError" title="exceptions.ValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ValueError</span></code></a>.</p> </dd></dl> <p>Example usage:</p> <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">StringIO</span> <span class="n">output</span> <span class="o">=</span> <span class="n">StringIO</span><span class="o">.</span><span class="n">StringIO</span><span class="p">()</span> <span class="n">output</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s1">'First line.</span><span class="se">\n</span><span class="s1">'</span><span class="p">)</span> <span class="nb">print</span> <span class="o">>></span><span class="n">output</span><span class="p">,</span> <span class="s1">'Second line.'</span> <span class="c1"># Retrieve file contents -- this will be</span> <span class="c1"># 'First line.\nSecond line.\n'</span> <span class="n">contents</span> <span class="o">=</span> <span class="n">output</span><span class="o">.</span><span class="n">getvalue</span><span class="p">()</span> <span class="c1"># Close object and discard memory buffer --</span> <span class="c1"># .getvalue() will now raise an exception.</span> <span class="n">output</span><span class="o">.</span><span class="n">close</span><span class="p">()</span> </pre></div> </div> </div> <div class="section" id="module-cStringIO"> <span id="cstringio-faster-version-of-stringio"></span><h1>7.6. <a class="reference internal" href="#module-cStringIO" title="cStringIO: Faster version of StringIO, but not subclassable."><code class="xref py py-mod docutils literal notranslate"><span class="pre">cStringIO</span></code></a> — Faster version of <a class="reference internal" href="#module-StringIO" title="StringIO: Read and write strings as if they were files."><code class="xref py py-mod docutils literal notranslate"><span class="pre">StringIO</span></code></a><a class="headerlink" href="#module-cStringIO" title="Permalink to this headline">¶</a></h1> <p>The module <a class="reference internal" href="#module-cStringIO" title="cStringIO: Faster version of StringIO, but not subclassable."><code class="xref py py-mod docutils literal notranslate"><span class="pre">cStringIO</span></code></a> provides an interface similar to that of the <a class="reference internal" href="#module-StringIO" title="StringIO: Read and write strings as if they were files."><code class="xref py py-mod docutils literal notranslate"><span class="pre">StringIO</span></code></a> module. Heavy use of <a class="reference internal" href="#StringIO.StringIO" title="StringIO.StringIO"><code class="xref py py-class docutils literal notranslate"><span class="pre">StringIO.StringIO</span></code></a> objects can be made more efficient by using the function <a class="reference internal" href="#module-StringIO" title="StringIO: Read and write strings as if they were files."><code class="xref py py-func docutils literal notranslate"><span class="pre">StringIO()</span></code></a> from this module instead.</p> <dl class="function"> <dt id="cStringIO.StringIO"> <code class="descclassname">cStringIO.</code><code class="descname">StringIO</code><span class="sig-paren">(</span><span class="optional">[</span><em>s</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#cStringIO.StringIO" title="Permalink to this definition">¶</a></dt> <dd><p>Return a StringIO-like stream for reading or writing.</p> <p>Since this is a factory function which returns objects of built-in types, there’s no way to build your own version using subclassing. It’s not possible to set attributes on it. Use the original <a class="reference internal" href="#module-StringIO" title="StringIO: Read and write strings as if they were files."><code class="xref py py-mod docutils literal notranslate"><span class="pre">StringIO</span></code></a> module in those cases.</p> <p>Unlike the <a class="reference internal" href="#module-StringIO" title="StringIO: Read and write strings as if they were files."><code class="xref py py-mod docutils literal notranslate"><span class="pre">StringIO</span></code></a> module, this module is not able to accept Unicode strings that cannot be encoded as plain ASCII strings.</p> <p>Another difference from the <a class="reference internal" href="#module-StringIO" title="StringIO: Read and write strings as if they were files."><code class="xref py py-mod docutils literal notranslate"><span class="pre">StringIO</span></code></a> module is that calling <a class="reference internal" href="#module-StringIO" title="StringIO: Read and write strings as if they were files."><code class="xref py py-func docutils literal notranslate"><span class="pre">StringIO()</span></code></a> with a string parameter creates a read-only object. Unlike an object created without a string parameter, it does not have write methods. These objects are not generally visible. They turn up in tracebacks as <code class="xref py py-class docutils literal notranslate"><span class="pre">StringI</span></code> and <code class="xref py py-class docutils literal notranslate"><span class="pre">StringO</span></code>.</p> </dd></dl> <p>The following data objects are provided as well:</p> <dl class="data"> <dt id="cStringIO.InputType"> <code class="descclassname">cStringIO.</code><code class="descname">InputType</code><a class="headerlink" href="#cStringIO.InputType" title="Permalink to this definition">¶</a></dt> <dd><p>The type object of the objects created by calling <a class="reference internal" href="#module-StringIO" title="StringIO: Read and write strings as if they were files."><code class="xref py py-func docutils literal notranslate"><span class="pre">StringIO()</span></code></a> with a string parameter.</p> </dd></dl> <dl class="data"> <dt id="cStringIO.OutputType"> <code class="descclassname">cStringIO.</code><code class="descname">OutputType</code><a class="headerlink" href="#cStringIO.OutputType" title="Permalink to this definition">¶</a></dt> <dd><p>The type object of the objects returned by calling <a class="reference internal" href="#module-StringIO" title="StringIO: Read and write strings as if they were files."><code class="xref py py-func docutils literal notranslate"><span class="pre">StringIO()</span></code></a> with no parameters.</p> </dd></dl> <p>There is a C API to the module as well; refer to the module source for more information.</p> <p>Example usage:</p> <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">cStringIO</span> <span class="n">output</span> <span class="o">=</span> <span class="n">cStringIO</span><span class="o">.</span><span class="n">StringIO</span><span class="p">()</span> <span class="n">output</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s1">'First line.</span><span class="se">\n</span><span class="s1">'</span><span class="p">)</span> <span class="nb">print</span> <span class="o">>></span><span class="n">output</span><span class="p">,</span> <span class="s1">'Second line.'</span> <span class="c1"># Retrieve file contents -- this will be</span> <span class="c1"># 'First line.\nSecond line.\n'</span> <span class="n">contents</span> <span class="o">=</span> <span class="n">output</span><span class="o">.</span><span class="n">getvalue</span><span class="p">()</span> <span class="c1"># Close object and discard memory buffer --</span> <span class="c1"># .getvalue() will now raise an exception.</span> <span class="n">output</span><span class="o">.</span><span class="n">close</span><span class="p">()</span> </pre></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="#">7.5. <code class="docutils literal notranslate"><span class="pre">StringIO</span></code> — Read and write strings as files</a></li> <li><a class="reference internal" href="#module-cStringIO">7.6. <code class="docutils literal notranslate"><span class="pre">cStringIO</span></code> — Faster version of <code class="docutils literal notranslate"><span class="pre">StringIO</span></code></a></li> </ul> <h4>Previous topic</h4> <p class="topless"><a href="difflib.html" title="previous chapter">7.4. <code class="docutils literal notranslate"><span class="pre">difflib</span></code> — Helpers for computing deltas</a></p> <h4>Next topic</h4> <p class="topless"><a href="textwrap.html" title="next chapter">7.7. <code class="docutils literal notranslate"><span class="pre">textwrap</span></code> — Text wrapping and filling</a></p> <div role="note" aria-label="source link"> <h3>This Page</h3> <ul class="this-page-menu"> <li><a href="../_sources/library/stringio.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="textwrap.html" title="7.7. textwrap — Text wrapping and filling" >next</a> |</li> <li class="right" > <a href="difflib.html" title="7.4. difflib — Helpers for computing deltas" >previous</a> |</li> <li><img src="../_static/py.png" alt="" style="vertical-align: middle; 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