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<div class="section" id="module-gzip">
<h1>12.2. <tt class="xref docutils literal"><span class="pre">gzip</span></tt> — Support for <strong>gzip</strong> files<a class="headerlink" href="#module-gzip" title="Permalink to this headline">¶</a></h1>
<p>This module provides a simple interface to compress and decompress files just
like the GNU programs <strong>gzip</strong> and <strong>gunzip</strong> would.</p>
<p>The data compression is provided by the <a title="Low-level interface to compression and decompression routines compatible with gzip." class="reference external" href="zlib.html#module-zlib"><tt class="xref docutils literal"><span class="pre">zlib</span></tt></a> module.</p>
<p>The <tt class="xref docutils literal"><span class="pre">gzip</span></tt> module provides the <a title="gzip.GzipFile" class="reference internal" href="#gzip.GzipFile"><tt class="xref docutils literal"><span class="pre">GzipFile</span></tt></a> class which is modeled
after Python’s File Object. The <a title="gzip.GzipFile" class="reference internal" href="#gzip.GzipFile"><tt class="xref docutils literal"><span class="pre">GzipFile</span></tt></a> class reads and writes
<strong>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>gzip</strong> and <strong>gunzip</strong> programs, such as those produced by
<strong>compress</strong> and <strong>pack</strong>, are not supported by this module.</p>
<p>For other archive formats, see the <a title="Interface to compression and decompression routines compatible with bzip2." class="reference external" href="bz2.html#module-bz2"><tt class="xref docutils literal"><span class="pre">bz2</span></tt></a>, <a title="Read and write ZIP-format archive files." class="reference external" href="zipfile.html#module-zipfile"><tt class="xref docutils literal"><span class="pre">zipfile</span></tt></a>, and
<a title="Read and write tar-format archive files." class="reference external" href="tarfile.html#module-tarfile"><tt class="xref docutils literal"><span class="pre">tarfile</span></tt></a> modules.</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><em>filename=None</em>, <em>mode=None</em>, <em>compresslevel=9</em>, <em>fileobj=None</em>, <em>mtime=None</em><big>)</big><a class="headerlink" href="#gzip.GzipFile" title="Permalink to this definition">¶</a></dt>
<dd><p>Constructor for the <a title="gzip.GzipFile" class="reference internal" href="#gzip.GzipFile"><tt class="xref 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 docutils literal"><span class="pre">readinto()</span></tt> and
<tt class="xref 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
<tt class="xref docutils literal"><span class="pre">StringIO</span></tt> object, or any other object which simulates a file. It
defaults to <tt class="xref 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="xref docutils literal"><span class="pre">None</span></tt>, the <em>filename</em> argument is only used to be
included in the <strong>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">1</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. 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>gzip</strong> compressed streams are
required to contain a timestamp. If omitted or <tt class="xref 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>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> member of the object returned
by <tt class="docutils literal"><span class="pre">os.stat()</span></tt>.</p>
<p>Calling a <a title="gzip.GzipFile" class="reference internal" href="#gzip.GzipFile"><tt class="xref docutils literal"><span class="pre">GzipFile</span></tt></a> object’s <tt class="xref 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 <tt class="xref docutils literal"><span class="pre">StringIO</span></tt> object opened for
writing as <em>fileobj</em>, and retrieve the resulting memory buffer using the
<tt class="xref docutils literal"><span class="pre">StringIO</span></tt> object’s <tt class="xref docutils literal"><span class="pre">getvalue()</span></tt> method.</p>
<p><a title="gzip.GzipFile" class="reference internal" href="#gzip.GzipFile"><tt class="xref docutils literal"><span class="pre">GzipFile</span></tt></a> supports the <a class="reference external" href="../reference/compound_stmts.html#with"><tt class="xref docutils literal"><span class="pre">with</span></tt></a> statement.</p>
<p>
<span class="versionmodified">Changed in version 3.1: </span>Support for the <a class="reference external" href="../reference/compound_stmts.html#with"><tt class="xref docutils literal"><span class="pre">with</span></tt></a> statement 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>, <em>mode='rb'</em>, <em>compresslevel=9</em><big>)</big><a class="headerlink" href="#gzip.open" title="Permalink to this definition">¶</a></dt>
<dd>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>.</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-python3"><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">'/home/joe/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-python3"><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">'/home/joe/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-python3"><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">'/home/joe/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">'/home/joe/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 title="Low-level interface to compression and decompression routines compatible with gzip." class="reference external" href="zlib.html#module-zlib"><tt class="xref docutils literal"><span class="pre">zlib</span></tt></a></dt>
<dd>The basic data compression module needed to support the <strong>gzip</strong> file
format.</dd>
</dl>
</div>
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<h3><a href="../contents.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference external" href="">12.2. <tt class="docutils literal"><span class="pre">gzip</span></tt> — Support for <strong>gzip</strong> files</a><ul>
<li><a class="reference external" 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 docutils literal"><span class="pre">zlib</span></tt> — Compression compatible with <strong>gzip</strong></a></p>
<h4>Next topic</h4>
<p class="topless"><a href="bz2.html"
title="next chapter">12.3. <tt class="docutils literal docutils literal"><span class="pre">bz2</span></tt> — Compression compatible with <strong>bzip2</strong></a></p>
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