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<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."><code class="xref py py-mod docutils literal notranslate"><span class="pre">gzip</span></code></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="https://github.com/python/cpython/tree/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."><code class="xref py py-mod docutils literal notranslate"><span class="pre">zlib</span></code></a> module.</p>
<p>The <a class="reference internal" href="#module-gzip" title="gzip: Interfaces for gzip compression and decompression using file objects."><code class="xref py py-mod docutils literal notranslate"><span class="pre">gzip</span></code></a> module provides the <a class="reference internal" href="#gzip.GzipFile" title="gzip.GzipFile"><code class="xref py py-class docutils literal notranslate"><span class="pre">GzipFile</span></code></a> class which is modeled
after Python’s File Object. The <a class="reference internal" href="#gzip.GzipFile" title="gzip.GzipFile"><code class="xref py py-class docutils literal notranslate"><span class="pre">GzipFile</span></code></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><code class="descclassname">gzip.</code><code class="descname">GzipFile</code><span class="sig-paren">(</span><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><span class="sig-paren">)</span><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"><code class="xref py py-class docutils literal notranslate"><span class="pre">GzipFile</span></code></a> class, which simulates most of the methods
of a file object, with the exception of the <code class="xref py py-meth docutils literal notranslate"><span class="pre">readinto()</span></code> and
<code class="xref py py-meth docutils literal notranslate"><span class="pre">truncate()</span></code> 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#StringIO.StringIO" title="StringIO.StringIO"><code class="xref py py-class docutils literal notranslate"><span class="pre">StringIO</span></code></a> object, or any other object which simulates a file. It
defaults to <code class="docutils literal notranslate"><span class="pre">None</span></code>, in which case <em>filename</em> is opened to provide a file
object.</p>
<p>When <em>fileobj</em> is not <code class="docutils literal notranslate"><span class="pre">None</span></code>, the <em>filename</em> argument is only used to be
included in the <strong class="program">gzip</strong> file header, which may include 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 <code class="docutils literal notranslate"><span class="pre">'r'</span></code>, <code class="docutils literal notranslate"><span class="pre">'rb'</span></code>, <code class="docutils literal notranslate"><span class="pre">'a'</span></code>, <code class="docutils literal notranslate"><span class="pre">'ab'</span></code>, <code class="docutils literal notranslate"><span class="pre">'w'</span></code>,
or <code class="docutils literal notranslate"><span class="pre">'wb'</span></code>, 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 <code class="docutils literal notranslate"><span class="pre">'rb'</span></code>. 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 <code class="docutils literal notranslate"><span class="pre">0</span></code> to <code class="docutils literal notranslate"><span class="pre">9</span></code> controlling
the level of compression; <code class="docutils literal notranslate"><span class="pre">1</span></code> is fastest and produces the least
compression, and <code class="docutils literal notranslate"><span class="pre">9</span></code> is slowest and produces the most compression. <code class="docutils literal notranslate"><span class="pre">0</span></code>
is no compression. The default is <code class="docutils literal notranslate"><span class="pre">9</span></code>.</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 <code class="docutils literal notranslate"><span class="pre">None</span></code>, 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
<code class="docutils literal notranslate"><span class="pre">time.time()</span></code> and of the <code class="docutils literal notranslate"><span class="pre">st_mtime</span></code> attribute of the object returned
by <code class="docutils literal notranslate"><span class="pre">os.stat()</span></code>.</p>
<p>Calling a <a class="reference internal" href="#gzip.GzipFile" title="gzip.GzipFile"><code class="xref py py-class docutils literal notranslate"><span class="pre">GzipFile</span></code></a> object’s <code class="xref py py-meth docutils literal notranslate"><span class="pre">close()</span></code> 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#StringIO.StringIO" title="StringIO.StringIO"><code class="xref py py-class docutils literal notranslate"><span class="pre">StringIO</span></code></a> object opened for
writing as <em>fileobj</em>, and retrieve the resulting memory buffer using the
<a class="reference internal" href="stringio.html#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.html#StringIO.StringIO.getvalue" title="StringIO.StringIO.getvalue"><code class="xref py py-meth docutils literal notranslate"><span class="pre">getvalue()</span></code></a> method.</p>
<p><a class="reference internal" href="#gzip.GzipFile" title="gzip.GzipFile"><code class="xref py py-class docutils literal notranslate"><span class="pre">GzipFile</span></code></a> supports iteration and the <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">with</span></code></a> statement.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 2.7: </span>Support for the <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">with</span></code></a> statement was added.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 2.7: </span>Support for zero-padded files was added.</p>
</div>
<div class="versionadded">
<p><span class="versionmodified added">New in version 2.7: </span>The <em>mtime</em> argument.</p>
</div>
</dd></dl>
<dl class="function">
<dt id="gzip.open">
<code class="descclassname">gzip.</code><code class="descname">open</code><span class="sig-paren">(</span><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><span class="sig-paren">)</span><a class="headerlink" href="#gzip.open" title="Permalink to this definition">¶</a></dt>
<dd><p>This is a shorthand for <code class="docutils literal notranslate"><span class="pre">GzipFile(filename,</span></code> <code class="docutils literal notranslate"><span class="pre">mode,</span></code> <code class="docutils literal notranslate"><span class="pre">compresslevel)</span></code>.
The <em>filename</em> argument is required; <em>mode</em> defaults to <code class="docutils literal notranslate"><span class="pre">'rb'</span></code> and
<em>compresslevel</em> defaults to <code class="docutils literal notranslate"><span class="pre">9</span></code>.</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-default notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">gzip</span>
<span class="k">with</span> <span class="n">gzip</span><span class="o">.</span><span class="n">open</span><span class="p">(</span><span class="s1">'file.txt.gz'</span><span class="p">,</span> <span class="s1">'rb'</span><span class="p">)</span> <span class="k">as</span> <span class="n">f</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>
</pre></div>
</div>
<p>Example of how to create a compressed GZIP file:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">gzip</span>
<span class="n">content</span> <span class="o">=</span> <span class="s2">"Lots of content here"</span>
<span class="k">with</span> <span class="n">gzip</span><span class="o">.</span><span class="n">open</span><span class="p">(</span><span class="s1">'file.txt.gz'</span><span class="p">,</span> <span class="s1">'wb'</span><span class="p">)</span> <span class="k">as</span> <span class="n">f</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>
</pre></div>
</div>
<p>Example of how to GZIP compress an existing file:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">gzip</span>
<span class="kn">import</span> <span class="nn">shutil</span>
<span class="k">with</span> <span class="nb">open</span><span class="p">(</span><span class="s1">'file.txt'</span><span class="p">,</span> <span class="s1">'rb'</span><span class="p">)</span> <span class="k">as</span> <span class="n">f_in</span><span class="p">,</span> <span class="n">gzip</span><span class="o">.</span><span class="n">open</span><span class="p">(</span><span class="s1">'file.txt.gz'</span><span class="p">,</span> <span class="s1">'wb'</span><span class="p">)</span> <span class="k">as</span> <span class="n">f_out</span><span class="p">:</span>
<span class="n">shutil</span><span class="o">.</span><span class="n">copyfileobj</span><span class="p">(</span><span class="n">f_in</span><span class="p">,</span> <span class="n">f_out</span><span class="p">)</span>
</pre></div>
</div>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<dl class="simple">
<dt>Module <a class="reference internal" href="zlib.html#module-zlib" title="zlib: Low-level interface to compression and decompression routines compatible with gzip."><code class="xref py py-mod docutils literal notranslate"><span class="pre">zlib</span></code></a></dt><dd><p>The basic data compression module needed to support the <strong class="program">gzip</strong> file
format.</p>
</dd>
</dl>
</div>
</div>
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<ul>
<li><a class="reference internal" href="#">12.2. <code class="xref py py-mod docutils literal notranslate"><span class="pre">gzip</span></code> — 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>
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