Edit File: gzip.html
<!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>12.2. gzip — Support for gzip files — Python 2.7.5 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: '2.7.5', COLLAPSE_INDEX: false, FILE_SUFFIX: '.html', HAS_SOURCE: true }; </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/sidebar.js"></script> <link rel="search" type="application/opensearchdescription+xml" title="Search within Python 2.7.5 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 2.7.5 documentation" href="../index.html" /> <link rel="up" title="12. Data Compression and Archiving" href="archiving.html" /> <link rel="next" title="12.3. bz2 — Compression compatible with bzip2" href="bz2.html" /> <link rel="prev" title="12.1. zlib — Compression compatible with gzip" href="zlib.html" /> <link rel="shortcut icon" type="image/png" href="../_static/py.png" /> <script type="text/javascript" src="../_static/copybutton.js"></script> </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="../py-modindex.html" title="Python Module Index" >modules</a> |</li> <li class="right" > <a href="bz2.html" title="12.3. bz2 — Compression compatible with bzip2" accesskey="N">next</a> |</li> <li class="right" > <a href="zlib.html" title="12.1. zlib — Compression compatible with gzip" accesskey="P">previous</a> |</li> <li><img src="../_static/py.png" alt="" style="vertical-align: middle; margin-top: -1px"/></li> <li><a href="http://www.python.org/">Python</a> »</li> <li> <a href="../index.html">Python 2.7.5 documentation</a> » </li> <li><a href="index.html" >The Python Standard Library</a> »</li> <li><a href="archiving.html" accesskey="U">12. Data Compression and Archiving</a> »</li> </ul> </div> <div class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body"> <div class="section" id="module-gzip"> <span id="gzip-support-for-gzip-files"></span><h1>12.2. <a class="reference internal" href="#module-gzip" title="gzip: Interfaces for gzip compression and decompression using file objects."><tt class="xref py py-mod docutils literal"><span class="pre">gzip</span></tt></a> — Support for <strong class="program">gzip</strong> files<a class="headerlink" href="#module-gzip" title="Permalink to this headline">¶</a></h1> <p><strong>Source code:</strong> <a class="reference external" href="http://hg.python.org/cpython/file/2.7/Lib/gzip.py">Lib/gzip.py</a></p> <hr class="docutils" /> <p>This module provides a simple interface to compress and decompress files just like the GNU programs <strong class="program">gzip</strong> and <strong class="program">gunzip</strong> would.</p> <p>The data compression is provided by the <a class="reference internal" href="zlib.html#module-zlib" title="zlib: Low-level interface to compression and decompression routines compatible with gzip."><tt class="xref py py-mod docutils literal"><span class="pre">zlib</span></tt></a> module.</p> <p>The <a class="reference internal" href="#module-gzip" title="gzip: Interfaces for gzip compression and decompression using file objects."><tt class="xref py py-mod docutils literal"><span class="pre">gzip</span></tt></a> module provides the <a class="reference internal" href="#gzip.GzipFile" title="gzip.GzipFile"><tt class="xref py py-class docutils literal"><span class="pre">GzipFile</span></tt></a> class which is modeled after Python’s File Object. The <a class="reference internal" href="#gzip.GzipFile" title="gzip.GzipFile"><tt class="xref py py-class docutils literal"><span class="pre">GzipFile</span></tt></a> class reads and writes <strong class="program">gzip</strong>-format files, automatically compressing or decompressing the data so that it looks like an ordinary file object.</p> <p>Note that additional file formats which can be decompressed by the <strong class="program">gzip</strong> and <strong class="program">gunzip</strong> programs, such as those produced by <strong class="program">compress</strong> and <strong class="program">pack</strong>, are not supported by this module.</p> <p>The module defines the following items:</p> <dl class="class"> <dt id="gzip.GzipFile"> <em class="property">class </em><tt class="descclassname">gzip.</tt><tt class="descname">GzipFile</tt><big>(</big><span class="optional">[</span><em>filename</em><span class="optional">[</span>, <em>mode</em><span class="optional">[</span>, <em>compresslevel</em><span class="optional">[</span>, <em>fileobj</em><span class="optional">[</span>, <em>mtime</em><span class="optional">]</span><span class="optional">]</span><span class="optional">]</span><span class="optional">]</span><span class="optional">]</span><big>)</big><a class="headerlink" href="#gzip.GzipFile" title="Permalink to this definition">¶</a></dt> <dd><p>Constructor for the <a class="reference internal" href="#gzip.GzipFile" title="gzip.GzipFile"><tt class="xref py py-class docutils literal"><span class="pre">GzipFile</span></tt></a> class, which simulates most of the methods of a file object, with the exception of the <tt class="xref py py-meth docutils literal"><span class="pre">readinto()</span></tt> and <tt class="xref py py-meth docutils literal"><span class="pre">truncate()</span></tt> methods. At least one of <em>fileobj</em> and <em>filename</em> must be given a non-trivial value.</p> <p>The new class instance is based on <em>fileobj</em>, which can be a regular file, a <a class="reference internal" href="stringio.html#module-StringIO" title="StringIO: Read and write strings as if they were files."><tt class="xref py py-class docutils literal"><span class="pre">StringIO</span></tt></a> object, or any other object which simulates a file. It defaults to <tt class="docutils literal"><span class="pre">None</span></tt>, in which case <em>filename</em> is opened to provide a file object.</p> <p>When <em>fileobj</em> is not <tt class="docutils literal"><span class="pre">None</span></tt>, the <em>filename</em> argument is only used to be included in the <strong class="program">gzip</strong> file header, which may includes the original filename of the uncompressed file. It defaults to the filename of <em>fileobj</em>, if discernible; otherwise, it defaults to the empty string, and in this case the original filename is not included in the header.</p> <p>The <em>mode</em> argument can be any of <tt class="docutils literal"><span class="pre">'r'</span></tt>, <tt class="docutils literal"><span class="pre">'rb'</span></tt>, <tt class="docutils literal"><span class="pre">'a'</span></tt>, <tt class="docutils literal"><span class="pre">'ab'</span></tt>, <tt class="docutils literal"><span class="pre">'w'</span></tt>, or <tt class="docutils literal"><span class="pre">'wb'</span></tt>, depending on whether the file will be read or written. The default is the mode of <em>fileobj</em> if discernible; otherwise, the default is <tt class="docutils literal"><span class="pre">'rb'</span></tt>. If not given, the ‘b’ flag will be added to the mode to ensure the file is opened in binary mode for cross-platform portability.</p> <p>The <em>compresslevel</em> argument is an integer from <tt class="docutils literal"><span class="pre">0</span></tt> to <tt class="docutils literal"><span class="pre">9</span></tt> controlling the level of compression; <tt class="docutils literal"><span class="pre">1</span></tt> is fastest and produces the least compression, and <tt class="docutils literal"><span class="pre">9</span></tt> is slowest and produces the most compression. <tt class="docutils literal"><span class="pre">0</span></tt> is no compression. The default is <tt class="docutils literal"><span class="pre">9</span></tt>.</p> <p>The <em>mtime</em> argument is an optional numeric timestamp to be written to the stream when compressing. All <strong class="program">gzip</strong> compressed streams are required to contain a timestamp. If omitted or <tt class="docutils literal"><span class="pre">None</span></tt>, the current time is used. This module ignores the timestamp when decompressing; however, some programs, such as <strong class="program">gunzip</strong>, make use of it. The format of the timestamp is the same as that of the return value of <tt class="docutils literal"><span class="pre">time.time()</span></tt> and of the <tt class="docutils literal"><span class="pre">st_mtime</span></tt> attribute of the object returned by <tt class="docutils literal"><span class="pre">os.stat()</span></tt>.</p> <p>Calling a <a class="reference internal" href="#gzip.GzipFile" title="gzip.GzipFile"><tt class="xref py py-class docutils literal"><span class="pre">GzipFile</span></tt></a> object’s <tt class="xref py py-meth docutils literal"><span class="pre">close()</span></tt> method does not close <em>fileobj</em>, since you might wish to append more material after the compressed data. This also allows you to pass a <a class="reference internal" href="stringio.html#module-StringIO" title="StringIO: Read and write strings as if they were files."><tt class="xref py py-class docutils literal"><span class="pre">StringIO</span></tt></a> object opened for writing as <em>fileobj</em>, and retrieve the resulting memory buffer using the <a class="reference internal" href="stringio.html#module-StringIO" title="StringIO: Read and write strings as if they were files."><tt class="xref py py-class docutils literal"><span class="pre">StringIO</span></tt></a> object’s <tt class="xref py py-meth docutils literal"><span class="pre">getvalue()</span></tt> method.</p> <p><a class="reference internal" href="#gzip.GzipFile" title="gzip.GzipFile"><tt class="xref py py-class docutils literal"><span class="pre">GzipFile</span></tt></a> supports iteration and the <a class="reference internal" href="../reference/compound_stmts.html#with"><tt class="xref std std-keyword docutils literal"><span class="pre">with</span></tt></a> statement.</p> <p class="versionchanged"> <span class="versionmodified">Changed in version 2.7: </span>Support for the <a class="reference internal" href="../reference/compound_stmts.html#with"><tt class="xref std std-keyword docutils literal"><span class="pre">with</span></tt></a> statement was added.</p> <p class="versionchanged"> <span class="versionmodified">Changed in version 2.7: </span>Support for zero-padded files was added.</p> </dd></dl> <dl class="function"> <dt id="gzip.open"> <tt class="descclassname">gzip.</tt><tt class="descname">open</tt><big>(</big><em>filename</em><span class="optional">[</span>, <em>mode</em><span class="optional">[</span>, <em>compresslevel</em><span class="optional">]</span><span class="optional">]</span><big>)</big><a class="headerlink" href="#gzip.open" title="Permalink to this definition">¶</a></dt> <dd><p>This is a shorthand for <tt class="docutils literal"><span class="pre">GzipFile(filename,</span></tt> <tt class="docutils literal"><span class="pre">mode,</span></tt> <tt class="docutils literal"><span class="pre">compresslevel)</span></tt>. The <em>filename</em> argument is required; <em>mode</em> defaults to <tt class="docutils literal"><span class="pre">'rb'</span></tt> and <em>compresslevel</em> defaults to <tt class="docutils literal"><span class="pre">9</span></tt>.</p> </dd></dl> <div class="section" id="examples-of-usage"> <span id="gzip-usage-examples"></span><h2>12.2.1. Examples of usage<a class="headerlink" href="#examples-of-usage" title="Permalink to this headline">¶</a></h2> <p>Example of how to read a compressed file:</p> <div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">gzip</span> <span class="n">f</span> <span class="o">=</span> <span class="n">gzip</span><span class="o">.</span><span class="n">open</span><span class="p">(</span><span class="s">'file.txt.gz'</span><span class="p">,</span> <span class="s">'rb'</span><span class="p">)</span> <span class="n">file_content</span> <span class="o">=</span> <span class="n">f</span><span class="o">.</span><span class="n">read</span><span class="p">()</span> <span class="n">f</span><span class="o">.</span><span class="n">close</span><span class="p">()</span> </pre></div> </div> <p>Example of how to create a compressed GZIP file:</p> <div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">gzip</span> <span class="n">content</span> <span class="o">=</span> <span class="s">"Lots of content here"</span> <span class="n">f</span> <span class="o">=</span> <span class="n">gzip</span><span class="o">.</span><span class="n">open</span><span class="p">(</span><span class="s">'file.txt.gz'</span><span class="p">,</span> <span class="s">'wb'</span><span class="p">)</span> <span class="n">f</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="n">content</span><span class="p">)</span> <span class="n">f</span><span class="o">.</span><span class="n">close</span><span class="p">()</span> </pre></div> </div> <p>Example of how to GZIP compress an existing file:</p> <div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">gzip</span> <span class="n">f_in</span> <span class="o">=</span> <span class="nb">open</span><span class="p">(</span><span class="s">'file.txt'</span><span class="p">,</span> <span class="s">'rb'</span><span class="p">)</span> <span class="n">f_out</span> <span class="o">=</span> <span class="n">gzip</span><span class="o">.</span><span class="n">open</span><span class="p">(</span><span class="s">'file.txt.gz'</span><span class="p">,</span> <span class="s">'wb'</span><span class="p">)</span> <span class="n">f_out</span><span class="o">.</span><span class="n">writelines</span><span class="p">(</span><span class="n">f_in</span><span class="p">)</span> <span class="n">f_out</span><span class="o">.</span><span class="n">close</span><span class="p">()</span> <span class="n">f_in</span><span class="o">.</span><span class="n">close</span><span class="p">()</span> </pre></div> </div> <div class="admonition-see-also admonition seealso"> <p class="first admonition-title">See also</p> <dl class="last docutils"> <dt>Module <a class="reference internal" href="zlib.html#module-zlib" title="zlib: Low-level interface to compression and decompression routines compatible with gzip."><tt class="xref py py-mod docutils literal"><span class="pre">zlib</span></tt></a></dt> <dd>The basic data compression module needed to support the <strong class="program">gzip</strong> file format.</dd> </dl> </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 internal" href="#">12.2. <tt class="docutils literal"><span class="pre">gzip</span></tt> — Support for <strong class="program">gzip</strong> files</a><ul> <li><a class="reference internal" href="#examples-of-usage">12.2.1. Examples of usage</a></li> </ul> </li> </ul> <h4>Previous topic</h4> <p class="topless"><a href="zlib.html" title="previous chapter">12.1. <tt class="docutils literal"><span class="pre">zlib</span></tt> — Compression compatible with <strong class="program">gzip</strong></a></p> <h4>Next topic</h4> <p class="topless"><a href="bz2.html" title="next chapter">12.3. <tt class="docutils literal"><span class="pre">bz2</span></tt> — Compression compatible with <strong class="program">bzip2</strong></a></p> <h3>This Page</h3> <ul class="this-page-menu"> <li><a href="../bugs.html">Report a Bug</a></li> <li><a href="../_sources/library/gzip.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" /> <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="../py-modindex.html" title="Python Module Index" >modules</a> |</li> <li class="right" > <a href="bz2.html" title="12.3. bz2 — Compression compatible with bzip2" >next</a> |</li> <li class="right" > <a href="zlib.html" title="12.1. zlib — Compression compatible with gzip" >previous</a> |</li> <li><img src="../_static/py.png" alt="" style="vertical-align: middle; margin-top: -1px"/></li> <li><a href="http://www.python.org/">Python</a> »</li> <li> <a href="../index.html">Python 2.7.5 documentation</a> » </li> <li><a href="index.html" >The Python Standard Library</a> »</li> <li><a href="archiving.html" >12. Data Compression and Archiving</a> »</li> </ul> </div> <div class="footer"> © <a href="../copyright.html">Copyright</a> 1990-2020, 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 Oct 13, 2020. <a href="../bugs.html">Found a bug</a>? <br /> Created using <a href="http://sphinx.pocoo.org/">Sphinx</a> 1.1.3. </div> </body> </html>