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<li><a class="reference internal" href="#"><code class="xref py py-mod docutils literal notranslate"><span class="pre">compression.zstd</span></code> — Compression compatible with the Zstandard format</a><ul>
<li><a class="reference internal" href="#exceptions">Exceptions</a></li>
<li><a class="reference internal" href="#reading-and-writing-compressed-files">Reading and writing compressed files</a></li>
<li><a class="reference internal" href="#compressing-and-decompressing-data-in-memory">Compressing and decompressing data in memory</a></li>
<li><a class="reference internal" href="#zstandard-dictionaries">Zstandard dictionaries</a></li>
<li><a class="reference internal" href="#advanced-parameter-control">Advanced parameter control</a></li>
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  <section id="module-compression.zstd">
<span id="compression-zstd-compression-compatible-with-the-zstandard-format"></span><h1><code class="xref py py-mod docutils literal notranslate"><span class="pre">compression.zstd</span></code> — Compression compatible with the Zstandard format<a class="headerlink" href="#module-compression.zstd" title="Link to this heading">¶</a></h1>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.14.</span></p>
</div>
<p><strong>Source code:</strong> <a class="extlink-source reference external" href="https://github.com/python/cpython/tree/3.14/Lib/compression/zstd/__init__.py">Lib/compression/zstd/__init__.py</a></p>
<hr class="docutils" />
<p>This module provides classes and functions for compressing and decompressing
data using the Zstandard (or <em>zstd</em>) compression algorithm. The
<a class="reference external" href="https://facebook.github.io/zstd/doc/api_manual_latest.html">zstd manual</a>
describes Zstandard as “a fast lossless compression algorithm, targeting
real-time compression scenarios at zlib-level and better compression ratios.”
Also included is a file interface that supports reading and writing the
contents of <code class="docutils literal notranslate"><span class="pre">.zst</span></code> files created by the <strong class="program">zstd</strong> utility, as well as
raw zstd compressed streams.</p>
<p>The <code class="xref py py-mod docutils literal notranslate"><span class="pre">compression.zstd</span></code> module contains:</p>
<ul class="simple">
<li><p>The <a class="reference internal" href="#compression.zstd.open" title="compression.zstd.open"><code class="xref py py-func docutils literal notranslate"><span class="pre">open()</span></code></a> function and <a class="reference internal" href="#compression.zstd.ZstdFile" title="compression.zstd.ZstdFile"><code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdFile</span></code></a> class for reading and
writing compressed files.</p></li>
<li><p>The <a class="reference internal" href="#compression.zstd.ZstdCompressor" title="compression.zstd.ZstdCompressor"><code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdCompressor</span></code></a> and <a class="reference internal" href="#compression.zstd.ZstdDecompressor" title="compression.zstd.ZstdDecompressor"><code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdDecompressor</span></code></a> classes for
incremental (de)compression.</p></li>
<li><p>The <a class="reference internal" href="#compression.zstd.compress" title="compression.zstd.compress"><code class="xref py py-func docutils literal notranslate"><span class="pre">compress()</span></code></a> and <a class="reference internal" href="#compression.zstd.decompress" title="compression.zstd.decompress"><code class="xref py py-func docutils literal notranslate"><span class="pre">decompress()</span></code></a> functions for one-shot
(de)compression.</p></li>
<li><p>The <a class="reference internal" href="#compression.zstd.train_dict" title="compression.zstd.train_dict"><code class="xref py py-func docutils literal notranslate"><span class="pre">train_dict()</span></code></a> and <a class="reference internal" href="#compression.zstd.finalize_dict" title="compression.zstd.finalize_dict"><code class="xref py py-func docutils literal notranslate"><span class="pre">finalize_dict()</span></code></a> functions and the
<a class="reference internal" href="#compression.zstd.ZstdDict" title="compression.zstd.ZstdDict"><code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdDict</span></code></a> class to train and manage Zstandard dictionaries.</p></li>
<li><p>The <a class="reference internal" href="#compression.zstd.CompressionParameter" title="compression.zstd.CompressionParameter"><code class="xref py py-class docutils literal notranslate"><span class="pre">CompressionParameter</span></code></a>, <a class="reference internal" href="#compression.zstd.DecompressionParameter" title="compression.zstd.DecompressionParameter"><code class="xref py py-class docutils literal notranslate"><span class="pre">DecompressionParameter</span></code></a>, and
<a class="reference internal" href="#compression.zstd.Strategy" title="compression.zstd.Strategy"><code class="xref py py-class docutils literal notranslate"><span class="pre">Strategy</span></code></a> classes for setting advanced (de)compression parameters.</p></li>
</ul>
<p>This is an <a class="reference internal" href="../glossary.html#term-optional-module"><span class="xref std std-term">optional module</span></a>.
If it is missing from your copy of CPython,
look for documentation from your distributor (that is,
whoever provided Python to you).
If you are the distributor, see <a class="reference internal" href="../using/configure.html#optional-module-requirements"><span class="std std-ref">Requirements for optional modules</span></a>.</p>
<section id="exceptions">
<h2>Exceptions<a class="headerlink" href="#exceptions" title="Link to this heading">¶</a></h2>
<dl class="py exception">
<dt class="sig sig-object py" id="compression.zstd.ZstdError">
<em class="property"><span class="k"><span class="pre">exception</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">compression.zstd.</span></span><span class="sig-name descname"><span class="pre">ZstdError</span></span><a class="headerlink" href="#compression.zstd.ZstdError" title="Link to this definition">¶</a></dt>
<dd><p>This exception is raised when an error occurs during compression or
decompression, or while initializing the (de)compressor state.</p>
</dd></dl>

</section>
<section id="reading-and-writing-compressed-files">
<h2>Reading and writing compressed files<a class="headerlink" href="#reading-and-writing-compressed-files" title="Link to this heading">¶</a></h2>
<dl class="py function">
<dt class="sig sig-object py" id="compression.zstd.open">
<span class="sig-prename descclassname"><span class="pre">compression.zstd.</span></span><span class="sig-name descname"><span class="pre">open</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">file</span></span></em>, <em class="sig-param"><span class="positional-only-separator o"><abbr title="Positional-only parameter separator (PEP 570)"><span class="pre">/</span></abbr></span></em>, <em class="sig-param"><span class="n"><span class="pre">mode</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">'rb'</span></span></em>, <em class="sig-param"><span class="keyword-only-separator o"><abbr title="Keyword-only parameters separator (PEP 3102)"><span class="pre">*</span></abbr></span></em>, <em class="sig-param"><span class="n"><span class="pre">level</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">options</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">zstd_dict</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">encoding</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">errors</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">newline</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#compression.zstd.open" title="Link to this definition">¶</a></dt>
<dd><p>Open a Zstandard-compressed file in binary or text mode, returning a
<a class="reference internal" href="../glossary.html#term-file-object"><span class="xref std std-term">file object</span></a>.</p>
<p>The <em>file</em> argument can be either a file name (given as a
<a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a>, <a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> or <a class="reference internal" href="../glossary.html#term-path-like-object"><span class="xref std std-term">path-like</span></a>
object), in which case the named file is opened, or it can be an existing
file object to read from or write to.</p>
<p>The mode argument can be either <code class="docutils literal notranslate"><span class="pre">'rb'</span></code> for reading (default), <code class="docutils literal notranslate"><span class="pre">'wb'</span></code> for
overwriting, <code class="docutils literal notranslate"><span class="pre">'ab'</span></code> for appending, or <code class="docutils literal notranslate"><span class="pre">'xb'</span></code> for exclusive creation.
These can equivalently be given as <code class="docutils literal notranslate"><span class="pre">'r'</span></code>, <code class="docutils literal notranslate"><span class="pre">'w'</span></code>, <code class="docutils literal notranslate"><span class="pre">'a'</span></code>, and <code class="docutils literal notranslate"><span class="pre">'x'</span></code>
respectively. You may also open in text mode with <code class="docutils literal notranslate"><span class="pre">'rt'</span></code>, <code class="docutils literal notranslate"><span class="pre">'wt'</span></code>,
<code class="docutils literal notranslate"><span class="pre">'at'</span></code>, and <code class="docutils literal notranslate"><span class="pre">'xt'</span></code> respectively.</p>
<p>When reading, the <em>options</em> argument can be a dictionary providing advanced
decompression parameters; see <a class="reference internal" href="#compression.zstd.DecompressionParameter" title="compression.zstd.DecompressionParameter"><code class="xref py py-class docutils literal notranslate"><span class="pre">DecompressionParameter</span></code></a> for detailed
information about supported
parameters. The <em>zstd_dict</em> argument is a <a class="reference internal" href="#compression.zstd.ZstdDict" title="compression.zstd.ZstdDict"><code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdDict</span></code></a> instance to be
used during decompression. When reading, if the <em>level</em>
argument is not None, a <code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code> will be raised.</p>
<p>When writing, the <em>options</em> argument can be a dictionary
providing advanced compression parameters; see
<a class="reference internal" href="#compression.zstd.CompressionParameter" title="compression.zstd.CompressionParameter"><code class="xref py py-class docutils literal notranslate"><span class="pre">CompressionParameter</span></code></a> for detailed information about supported
parameters. The <em>level</em> argument is the compression level to use when
writing compressed data. Only one of <em>level</em> or <em>options</em> may be non-None.
The <em>zstd_dict</em> argument is a <a class="reference internal" href="#compression.zstd.ZstdDict" title="compression.zstd.ZstdDict"><code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdDict</span></code></a> instance to be used during
compression.</p>
<p>In binary mode, this function is equivalent to the <a class="reference internal" href="#compression.zstd.ZstdFile" title="compression.zstd.ZstdFile"><code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdFile</span></code></a>
constructor: <code class="docutils literal notranslate"><span class="pre">ZstdFile(file,</span> <span class="pre">mode,</span> <span class="pre">...)</span></code>. In this case, the
<em>encoding</em>, <em>errors</em>, and <em>newline</em> parameters must not be provided.</p>
<p>In text mode, a <a class="reference internal" href="#compression.zstd.ZstdFile" title="compression.zstd.ZstdFile"><code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdFile</span></code></a> object is created, and wrapped in an
<a class="reference internal" href="io.html#io.TextIOWrapper" title="io.TextIOWrapper"><code class="xref py py-class docutils literal notranslate"><span class="pre">io.TextIOWrapper</span></code></a> instance with the specified encoding, error
handling behavior, and line endings.</p>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="compression.zstd.ZstdFile">
<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">compression.zstd.</span></span><span class="sig-name descname"><span class="pre">ZstdFile</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">file</span></span></em>, <em class="sig-param"><span class="positional-only-separator o"><abbr title="Positional-only parameter separator (PEP 570)"><span class="pre">/</span></abbr></span></em>, <em class="sig-param"><span class="n"><span class="pre">mode</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">'rb'</span></span></em>, <em class="sig-param"><span class="keyword-only-separator o"><abbr title="Keyword-only parameters separator (PEP 3102)"><span class="pre">*</span></abbr></span></em>, <em class="sig-param"><span class="n"><span class="pre">level</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">options</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">zstd_dict</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#compression.zstd.ZstdFile" title="Link to this definition">¶</a></dt>
<dd><p>Open a Zstandard-compressed file in binary mode.</p>
<p>A <code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdFile</span></code> can wrap an already-open <a class="reference internal" href="../glossary.html#term-file-object"><span class="xref std std-term">file object</span></a>, or operate
directly on a named file. The <em>file</em> argument specifies either the file
object to wrap, or the name of the file to open (as a <a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a>,
<a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> or <a class="reference internal" href="../glossary.html#term-path-like-object"><span class="xref std std-term">path-like</span></a> object). If
wrapping an existing file object, the wrapped file will not be closed when
the <code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdFile</span></code> is closed.</p>
<p>The <em>mode</em> argument can be either <code class="docutils literal notranslate"><span class="pre">'rb'</span></code> for reading (default), <code class="docutils literal notranslate"><span class="pre">'wb'</span></code>
for overwriting, <code class="docutils literal notranslate"><span class="pre">'xb'</span></code> for exclusive creation, or <code class="docutils literal notranslate"><span class="pre">'ab'</span></code> for appending.
These can equivalently be given as <code class="docutils literal notranslate"><span class="pre">'r'</span></code>, <code class="docutils literal notranslate"><span class="pre">'w'</span></code>, <code class="docutils literal notranslate"><span class="pre">'x'</span></code> and <code class="docutils literal notranslate"><span class="pre">'a'</span></code>
respectively.</p>
<p>If <em>file</em> is a file object (rather than an actual file name), a mode of
<code class="docutils literal notranslate"><span class="pre">'w'</span></code> does not truncate the file, and is instead equivalent to <code class="docutils literal notranslate"><span class="pre">'a'</span></code>.</p>
<p>When reading, the <em>options</em> argument can be a dictionary
providing advanced decompression parameters; see
<a class="reference internal" href="#compression.zstd.DecompressionParameter" title="compression.zstd.DecompressionParameter"><code class="xref py py-class docutils literal notranslate"><span class="pre">DecompressionParameter</span></code></a> for detailed information about supported
parameters. The <em>zstd_dict</em> argument is a <a class="reference internal" href="#compression.zstd.ZstdDict" title="compression.zstd.ZstdDict"><code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdDict</span></code></a> instance to be
used during decompression. When reading, if the <em>level</em>
argument is not None, a <code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code> will be raised.</p>
<p>When writing, the <em>options</em> argument can be a dictionary
providing advanced compression parameters; see
<a class="reference internal" href="#compression.zstd.CompressionParameter" title="compression.zstd.CompressionParameter"><code class="xref py py-class docutils literal notranslate"><span class="pre">CompressionParameter</span></code></a> for detailed information about supported
parameters. The <em>level</em> argument is the compression level to use when
writing compressed data. Only one of <em>level</em> or <em>options</em> may be passed. The
<em>zstd_dict</em> argument is a <a class="reference internal" href="#compression.zstd.ZstdDict" title="compression.zstd.ZstdDict"><code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdDict</span></code></a> instance to be used during
compression.</p>
<p><code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdFile</span></code> supports all the members specified by
<a class="reference internal" href="io.html#io.BufferedIOBase" title="io.BufferedIOBase"><code class="xref py py-class docutils literal notranslate"><span class="pre">io.BufferedIOBase</span></code></a>, except for <a class="reference internal" href="io.html#io.BufferedIOBase.detach" title="io.BufferedIOBase.detach"><code class="xref py py-meth docutils literal notranslate"><span class="pre">detach()</span></code></a>
and <a class="reference internal" href="io.html#io.IOBase.truncate" title="io.IOBase.truncate"><code class="xref py py-meth docutils literal notranslate"><span class="pre">truncate()</span></code></a>.
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 are supported.</p>
<p>The following method and attributes are also provided:</p>
<dl class="py method">
<dt class="sig sig-object py" id="compression.zstd.ZstdFile.peek">
<span class="sig-name descname"><span class="pre">peek</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">size</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">-1</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#compression.zstd.ZstdFile.peek" title="Link to this definition">¶</a></dt>
<dd><p>Return buffered data without advancing the file position. At least one
byte of data will be returned, unless EOF has been reached. The exact
number of bytes returned is unspecified (the <em>size</em> argument is ignored).</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>While calling <code class="xref py py-meth docutils literal notranslate"><span class="pre">peek()</span></code> does not change the file position of
the <code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdFile</span></code>, it may change the position of the underlying
file object (for example, if the <code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdFile</span></code> was constructed by
passing a file object for <em>file</em>).</p>
</div>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.ZstdFile.mode">
<span class="sig-name descname"><span class="pre">mode</span></span><a class="headerlink" href="#compression.zstd.ZstdFile.mode" title="Link to this definition">¶</a></dt>
<dd><p><code class="docutils literal notranslate"><span class="pre">'rb'</span></code> for reading and <code class="docutils literal notranslate"><span class="pre">'wb'</span></code> for writing.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.ZstdFile.name">
<span class="sig-name descname"><span class="pre">name</span></span><a class="headerlink" href="#compression.zstd.ZstdFile.name" title="Link to this definition">¶</a></dt>
<dd><p>The name of the Zstandard file. Equivalent to the <a class="reference internal" href="io.html#io.FileIO.name" title="io.FileIO.name"><code class="xref py py-attr docutils literal notranslate"><span class="pre">name</span></code></a>
attribute of the underlying <a class="reference internal" href="../glossary.html#term-file-object"><span class="xref std std-term">file object</span></a>.</p>
</dd></dl>

</dd></dl>

</section>
<section id="compressing-and-decompressing-data-in-memory">
<h2>Compressing and decompressing data in memory<a class="headerlink" href="#compressing-and-decompressing-data-in-memory" title="Link to this heading">¶</a></h2>
<dl class="py function">
<dt class="sig sig-object py" id="compression.zstd.compress">
<span class="sig-prename descclassname"><span class="pre">compression.zstd.</span></span><span class="sig-name descname"><span class="pre">compress</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">data</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">level</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">options</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">zstd_dict</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#compression.zstd.compress" title="Link to this definition">¶</a></dt>
<dd><p>Compress <em>data</em> (a <a class="reference internal" href="../glossary.html#term-bytes-like-object"><span class="xref std std-term">bytes-like object</span></a>), returning the compressed
data as a <a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> object.</p>
<p>The <em>level</em> argument is an integer controlling the level of
compression. <em>level</em> is an alternative to setting
<a class="reference internal" href="#compression.zstd.CompressionParameter.compression_level" title="compression.zstd.CompressionParameter.compression_level"><code class="xref py py-attr docutils literal notranslate"><span class="pre">CompressionParameter.compression_level</span></code></a> in <em>options</em>. Use
<a class="reference internal" href="#compression.zstd.CompressionParameter.bounds" title="compression.zstd.CompressionParameter.bounds"><code class="xref py py-meth docutils literal notranslate"><span class="pre">bounds()</span></code></a> on
<code class="xref py py-attr docutils literal notranslate"><span class="pre">compression_level</span></code> to get the values that can
be passed for <em>level</em>. If advanced compression options are needed, the
<em>level</em> argument must be omitted and in the <em>options</em> dictionary the
<code class="xref py py-attr docutils literal notranslate"><span class="pre">CompressionParameter.compression_level</span></code> parameter should be set.</p>
<p>The <em>options</em> argument is a Python dictionary containing advanced
compression parameters. The valid keys and values for compression parameters
are documented as part of the <a class="reference internal" href="#compression.zstd.CompressionParameter" title="compression.zstd.CompressionParameter"><code class="xref py py-class docutils literal notranslate"><span class="pre">CompressionParameter</span></code></a> documentation.</p>
<p>The <em>zstd_dict</em> argument is an instance of <a class="reference internal" href="#compression.zstd.ZstdDict" title="compression.zstd.ZstdDict"><code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdDict</span></code></a>
containing trained data to improve compression efficiency. The
function <a class="reference internal" href="#compression.zstd.train_dict" title="compression.zstd.train_dict"><code class="xref py py-func docutils literal notranslate"><span class="pre">train_dict()</span></code></a> can be used to generate a Zstandard dictionary.</p>
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="compression.zstd.decompress">
<span class="sig-prename descclassname"><span class="pre">compression.zstd.</span></span><span class="sig-name descname"><span class="pre">decompress</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">data</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">zstd_dict</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">options</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#compression.zstd.decompress" title="Link to this definition">¶</a></dt>
<dd><p>Decompress <em>data</em> (a <a class="reference internal" href="../glossary.html#term-bytes-like-object"><span class="xref std std-term">bytes-like object</span></a>), returning the uncompressed
data as a <a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> object.</p>
<p>The <em>options</em> argument is a Python dictionary containing advanced
decompression parameters. The valid keys and values for compression
parameters are documented as part of the <a class="reference internal" href="#compression.zstd.DecompressionParameter" title="compression.zstd.DecompressionParameter"><code class="xref py py-class docutils literal notranslate"><span class="pre">DecompressionParameter</span></code></a>
documentation.</p>
<p>The <em>zstd_dict</em> argument is an instance of <a class="reference internal" href="#compression.zstd.ZstdDict" title="compression.zstd.ZstdDict"><code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdDict</span></code></a>
containing trained data used during compression. This must be
the same Zstandard dictionary used during compression.</p>
<p>If <em>data</em> is the concatenation of multiple distinct compressed frames,
decompress all of these frames, and return the concatenation of the results.</p>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="compression.zstd.ZstdCompressor">
<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">compression.zstd.</span></span><span class="sig-name descname"><span class="pre">ZstdCompressor</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">level</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">options</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">zstd_dict</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#compression.zstd.ZstdCompressor" title="Link to this definition">¶</a></dt>
<dd><p>Create a compressor object, which can be used to compress data
incrementally.</p>
<p>For a more convenient way of compressing a single chunk of data, see the
module-level function <a class="reference internal" href="#compression.zstd.compress" title="compression.zstd.compress"><code class="xref py py-func docutils literal notranslate"><span class="pre">compress()</span></code></a>.</p>
<p>The <em>level</em> argument is an integer controlling the level of
compression. <em>level</em> is an alternative to setting
<a class="reference internal" href="#compression.zstd.CompressionParameter.compression_level" title="compression.zstd.CompressionParameter.compression_level"><code class="xref py py-attr docutils literal notranslate"><span class="pre">CompressionParameter.compression_level</span></code></a> in <em>options</em>. Use
<a class="reference internal" href="#compression.zstd.CompressionParameter.bounds" title="compression.zstd.CompressionParameter.bounds"><code class="xref py py-meth docutils literal notranslate"><span class="pre">bounds()</span></code></a> on
<code class="xref py py-attr docutils literal notranslate"><span class="pre">compression_level</span></code> to get the values that can
be passed for <em>level</em>. If advanced compression options are needed, the
<em>level</em> argument must be omitted and in the <em>options</em> dictionary the
<code class="xref py py-attr docutils literal notranslate"><span class="pre">CompressionParameter.compression_level</span></code> parameter should be set.</p>
<p>The <em>options</em> argument is a Python dictionary containing advanced
compression parameters. The valid keys and values for compression parameters
are documented as part of the <a class="reference internal" href="#compression.zstd.CompressionParameter" title="compression.zstd.CompressionParameter"><code class="xref py py-class docutils literal notranslate"><span class="pre">CompressionParameter</span></code></a> documentation.</p>
<p>The <em>zstd_dict</em> argument is an optional instance of <a class="reference internal" href="#compression.zstd.ZstdDict" title="compression.zstd.ZstdDict"><code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdDict</span></code></a>
containing trained data to improve compression efficiency. The
function <a class="reference internal" href="#compression.zstd.train_dict" title="compression.zstd.train_dict"><code class="xref py py-func docutils literal notranslate"><span class="pre">train_dict()</span></code></a> can be used to generate a Zstandard dictionary.</p>
<dl class="py method">
<dt class="sig sig-object py" id="compression.zstd.ZstdCompressor.compress">
<span class="sig-name descname"><span class="pre">compress</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">data</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">mode</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">ZstdCompressor.CONTINUE</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#compression.zstd.ZstdCompressor.compress" title="Link to this definition">¶</a></dt>
<dd><p>Compress <em>data</em> (a <a class="reference internal" href="../glossary.html#term-bytes-like-object"><span class="xref std std-term">bytes-like object</span></a>), returning a <a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a>
object with compressed data if possible, or otherwise an empty
<code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code> object. Some of <em>data</em> may be buffered internally, for
use in later calls to <code class="xref py py-meth docutils literal notranslate"><span class="pre">compress()</span></code> and <a class="reference internal" href="#compression.zstd.ZstdCompressor.flush" title="compression.zstd.ZstdCompressor.flush"><code class="xref py py-meth docutils literal notranslate"><span class="pre">flush()</span></code></a>. The returned
data should be concatenated with the output of any previous calls to
<code class="xref py py-meth docutils literal notranslate"><span class="pre">compress()</span></code>.</p>
<p>The <em>mode</em> argument is a <code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdCompressor</span></code> attribute, either
<a class="reference internal" href="#compression.zstd.ZstdCompressor.CONTINUE" title="compression.zstd.ZstdCompressor.CONTINUE"><code class="xref py py-attr docutils literal notranslate"><span class="pre">CONTINUE</span></code></a>, <a class="reference internal" href="#compression.zstd.ZstdCompressor.FLUSH_BLOCK" title="compression.zstd.ZstdCompressor.FLUSH_BLOCK"><code class="xref py py-attr docutils literal notranslate"><span class="pre">FLUSH_BLOCK</span></code></a>,
or <a class="reference internal" href="#compression.zstd.ZstdCompressor.FLUSH_FRAME" title="compression.zstd.ZstdCompressor.FLUSH_FRAME"><code class="xref py py-attr docutils literal notranslate"><span class="pre">FLUSH_FRAME</span></code></a>.</p>
<p>When all data has been provided to the compressor, call the
<a class="reference internal" href="#compression.zstd.ZstdCompressor.flush" title="compression.zstd.ZstdCompressor.flush"><code class="xref py py-meth docutils literal notranslate"><span class="pre">flush()</span></code></a> method to finish the compression process. If
<code class="xref py py-meth docutils literal notranslate"><span class="pre">compress()</span></code> is called with <em>mode</em> set to <a class="reference internal" href="#compression.zstd.ZstdCompressor.FLUSH_FRAME" title="compression.zstd.ZstdCompressor.FLUSH_FRAME"><code class="xref py py-attr docutils literal notranslate"><span class="pre">FLUSH_FRAME</span></code></a>,
<code class="xref py py-meth docutils literal notranslate"><span class="pre">flush()</span></code> should not be called, as it would write out a new empty
frame.</p>
</dd></dl>

<dl class="py method">
<dt class="sig sig-object py" id="compression.zstd.ZstdCompressor.flush">
<span class="sig-name descname"><span class="pre">flush</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">mode</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">ZstdCompressor.FLUSH_FRAME</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#compression.zstd.ZstdCompressor.flush" title="Link to this definition">¶</a></dt>
<dd><p>Finish the compression process, returning a <a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> object
containing any data stored in the compressor’s internal buffers.</p>
<p>The <em>mode</em> argument is a <code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdCompressor</span></code> attribute, either
<a class="reference internal" href="#compression.zstd.ZstdCompressor.FLUSH_BLOCK" title="compression.zstd.ZstdCompressor.FLUSH_BLOCK"><code class="xref py py-attr docutils literal notranslate"><span class="pre">FLUSH_BLOCK</span></code></a>, or <a class="reference internal" href="#compression.zstd.ZstdCompressor.FLUSH_FRAME" title="compression.zstd.ZstdCompressor.FLUSH_FRAME"><code class="xref py py-attr docutils literal notranslate"><span class="pre">FLUSH_FRAME</span></code></a>.</p>
</dd></dl>

<dl class="py method">
<dt class="sig sig-object py" id="compression.zstd.ZstdCompressor.set_pledged_input_size">
<span class="sig-name descname"><span class="pre">set_pledged_input_size</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">size</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#compression.zstd.ZstdCompressor.set_pledged_input_size" title="Link to this definition">¶</a></dt>
<dd><p>Specify the amount of uncompressed data <em>size</em> that will be provided for
the next frame. <em>size</em> will be written into the frame header of the next
frame unless <a class="reference internal" href="#compression.zstd.CompressionParameter.content_size_flag" title="compression.zstd.CompressionParameter.content_size_flag"><code class="xref py py-attr docutils literal notranslate"><span class="pre">CompressionParameter.content_size_flag</span></code></a> is <code class="docutils literal notranslate"><span class="pre">False</span></code>
or <code class="docutils literal notranslate"><span class="pre">0</span></code>. A size of <code class="docutils literal notranslate"><span class="pre">0</span></code> means that the frame is empty. If <em>size</em> is
<code class="docutils literal notranslate"><span class="pre">None</span></code>, the frame header will omit the frame size. Frames that include
the uncompressed data size require less memory to decompress, especially
at higher compression levels.</p>
<p>If <a class="reference internal" href="#compression.zstd.ZstdCompressor.last_mode" title="compression.zstd.ZstdCompressor.last_mode"><code class="xref py py-attr docutils literal notranslate"><span class="pre">last_mode</span></code></a> is not <a class="reference internal" href="#compression.zstd.ZstdCompressor.FLUSH_FRAME" title="compression.zstd.ZstdCompressor.FLUSH_FRAME"><code class="xref py py-attr docutils literal notranslate"><span class="pre">FLUSH_FRAME</span></code></a>, a
<a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ValueError</span></code></a> is raised as the compressor is not at the start of
a frame. If the pledged size does not match the actual size of data
provided to <a class="reference internal" href="#compression.zstd.ZstdCompressor.compress" title="compression.zstd.ZstdCompressor.compress"><code class="xref py py-meth docutils literal notranslate"><span class="pre">compress()</span></code></a>, future calls to <code class="xref py py-meth docutils literal notranslate"><span class="pre">compress()</span></code> or
<a class="reference internal" href="#compression.zstd.ZstdCompressor.flush" title="compression.zstd.ZstdCompressor.flush"><code class="xref py py-meth docutils literal notranslate"><span class="pre">flush()</span></code></a> may raise <a class="reference internal" href="#compression.zstd.ZstdError" title="compression.zstd.ZstdError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ZstdError</span></code></a> and the last chunk of data may
be lost.</p>
<p>After <a class="reference internal" href="#compression.zstd.ZstdCompressor.flush" title="compression.zstd.ZstdCompressor.flush"><code class="xref py py-meth docutils literal notranslate"><span class="pre">flush()</span></code></a> or <a class="reference internal" href="#compression.zstd.ZstdCompressor.compress" title="compression.zstd.ZstdCompressor.compress"><code class="xref py py-meth docutils literal notranslate"><span class="pre">compress()</span></code></a> are called with mode
<a class="reference internal" href="#compression.zstd.ZstdCompressor.FLUSH_FRAME" title="compression.zstd.ZstdCompressor.FLUSH_FRAME"><code class="xref py py-attr docutils literal notranslate"><span class="pre">FLUSH_FRAME</span></code></a>, the next frame will not include the frame size into
the header unless <code class="xref py py-meth docutils literal notranslate"><span class="pre">set_pledged_input_size()</span></code> is called again.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.ZstdCompressor.CONTINUE">
<span class="sig-name descname"><span class="pre">CONTINUE</span></span><a class="headerlink" href="#compression.zstd.ZstdCompressor.CONTINUE" title="Link to this definition">¶</a></dt>
<dd><p>Collect more data for compression, which may or may not generate output
immediately. This mode optimizes the compression ratio by maximizing the
amount of data per block and frame.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.ZstdCompressor.FLUSH_BLOCK">
<span class="sig-name descname"><span class="pre">FLUSH_BLOCK</span></span><a class="headerlink" href="#compression.zstd.ZstdCompressor.FLUSH_BLOCK" title="Link to this definition">¶</a></dt>
<dd><p>Complete and write a block to the data stream. The data returned so far
can be immediately decompressed. Past data can still be referenced in
future blocks generated by calls to <a class="reference internal" href="#compression.zstd.ZstdCompressor.compress" title="compression.zstd.ZstdCompressor.compress"><code class="xref py py-meth docutils literal notranslate"><span class="pre">compress()</span></code></a>,
improving compression.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.ZstdCompressor.FLUSH_FRAME">
<span class="sig-name descname"><span class="pre">FLUSH_FRAME</span></span><a class="headerlink" href="#compression.zstd.ZstdCompressor.FLUSH_FRAME" title="Link to this definition">¶</a></dt>
<dd><p>Complete and write out a frame. Future data provided to
<a class="reference internal" href="#compression.zstd.ZstdCompressor.compress" title="compression.zstd.ZstdCompressor.compress"><code class="xref py py-meth docutils literal notranslate"><span class="pre">compress()</span></code></a> will be written into a new frame and
<em>cannot</em> reference past data.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.ZstdCompressor.last_mode">
<span class="sig-name descname"><span class="pre">last_mode</span></span><a class="headerlink" href="#compression.zstd.ZstdCompressor.last_mode" title="Link to this definition">¶</a></dt>
<dd><p>The last mode passed to either <a class="reference internal" href="#compression.zstd.ZstdCompressor.compress" title="compression.zstd.ZstdCompressor.compress"><code class="xref py py-meth docutils literal notranslate"><span class="pre">compress()</span></code></a> or <a class="reference internal" href="#compression.zstd.ZstdCompressor.flush" title="compression.zstd.ZstdCompressor.flush"><code class="xref py py-meth docutils literal notranslate"><span class="pre">flush()</span></code></a>.
The value can be one of <a class="reference internal" href="#compression.zstd.ZstdCompressor.CONTINUE" title="compression.zstd.ZstdCompressor.CONTINUE"><code class="xref py py-attr docutils literal notranslate"><span class="pre">CONTINUE</span></code></a>, <a class="reference internal" href="#compression.zstd.ZstdCompressor.FLUSH_BLOCK" title="compression.zstd.ZstdCompressor.FLUSH_BLOCK"><code class="xref py py-attr docutils literal notranslate"><span class="pre">FLUSH_BLOCK</span></code></a>, or
<a class="reference internal" href="#compression.zstd.ZstdCompressor.FLUSH_FRAME" title="compression.zstd.ZstdCompressor.FLUSH_FRAME"><code class="xref py py-attr docutils literal notranslate"><span class="pre">FLUSH_FRAME</span></code></a>. The initial value is <code class="xref py py-attr docutils literal notranslate"><span class="pre">FLUSH_FRAME</span></code>,
signifying that the compressor is at the start of a new frame.</p>
</dd></dl>

</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="compression.zstd.ZstdDecompressor">
<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">compression.zstd.</span></span><span class="sig-name descname"><span class="pre">ZstdDecompressor</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">zstd_dict</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">options</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#compression.zstd.ZstdDecompressor" title="Link to this definition">¶</a></dt>
<dd><p>Create a decompressor object, which can be used to decompress data
incrementally.</p>
<p>For a more convenient way of decompressing an entire compressed stream at
once, see the module-level function <a class="reference internal" href="#compression.zstd.decompress" title="compression.zstd.decompress"><code class="xref py py-func docutils literal notranslate"><span class="pre">decompress()</span></code></a>.</p>
<p>The <em>options</em> argument is a Python dictionary containing advanced
decompression parameters. The valid keys and values for compression
parameters are documented as part of the <a class="reference internal" href="#compression.zstd.DecompressionParameter" title="compression.zstd.DecompressionParameter"><code class="xref py py-class docutils literal notranslate"><span class="pre">DecompressionParameter</span></code></a>
documentation.</p>
<p>The <em>zstd_dict</em> argument is an instance of <a class="reference internal" href="#compression.zstd.ZstdDict" title="compression.zstd.ZstdDict"><code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdDict</span></code></a>
containing trained data used during compression. This must be
the same Zstandard dictionary used during compression.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>This class does not transparently handle inputs containing multiple
compressed frames, unlike the <a class="reference internal" href="#compression.zstd.decompress" title="compression.zstd.decompress"><code class="xref py py-func docutils literal notranslate"><span class="pre">decompress()</span></code></a> function and
<a class="reference internal" href="#compression.zstd.ZstdFile" title="compression.zstd.ZstdFile"><code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdFile</span></code></a> class. To decompress a multi-frame input, you should
use <code class="xref py py-func docutils literal notranslate"><span class="pre">decompress()</span></code>, <code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdFile</span></code> if working with a
<a class="reference internal" href="../glossary.html#term-file-object"><span class="xref std std-term">file object</span></a>, or multiple <code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdDecompressor</span></code> instances.</p>
</div>
<dl class="py method">
<dt class="sig sig-object py" id="compression.zstd.ZstdDecompressor.decompress">
<span class="sig-name descname"><span class="pre">decompress</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">data</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">max_length</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">-1</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#compression.zstd.ZstdDecompressor.decompress" title="Link to this definition">¶</a></dt>
<dd><p>Decompress <em>data</em> (a <a class="reference internal" href="../glossary.html#term-bytes-like-object"><span class="xref std std-term">bytes-like object</span></a>), returning
uncompressed data as bytes. Some of <em>data</em> may be buffered
internally, for use in later calls to <code class="xref py py-meth docutils literal notranslate"><span class="pre">decompress()</span></code>.
The returned data should be concatenated with the output of any previous
calls to <code class="xref py py-meth docutils literal notranslate"><span class="pre">decompress()</span></code>.</p>
<p>If <em>max_length</em> is non-negative, the method returns at most <em>max_length</em>
bytes of decompressed data. If this limit is reached and further
output can be produced, the <a class="reference internal" href="#compression.zstd.ZstdDecompressor.needs_input" title="compression.zstd.ZstdDecompressor.needs_input"><code class="xref py py-attr docutils literal notranslate"><span class="pre">needs_input</span></code></a> attribute will
be set to <code class="docutils literal notranslate"><span class="pre">False</span></code>. In this case, the next call to
<code class="xref py py-meth docutils literal notranslate"><span class="pre">decompress()</span></code> may provide <em>data</em> as <code class="docutils literal notranslate"><span class="pre">b''</span></code> to obtain
more of the output.</p>
<p>If all of the input data was decompressed and returned (either
because this was less than <em>max_length</em> bytes, or because
<em>max_length</em> was negative), the <a class="reference internal" href="#compression.zstd.ZstdDecompressor.needs_input" title="compression.zstd.ZstdDecompressor.needs_input"><code class="xref py py-attr docutils literal notranslate"><span class="pre">needs_input</span></code></a> attribute
will be set to <code class="docutils literal notranslate"><span class="pre">True</span></code>.</p>
<p>Attempting to decompress data after the end of a frame will raise a
<a class="reference internal" href="#compression.zstd.ZstdError" title="compression.zstd.ZstdError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ZstdError</span></code></a>. Any data found after the end of the frame is ignored
and saved in the <a class="reference internal" href="#compression.zstd.ZstdDecompressor.unused_data" title="compression.zstd.ZstdDecompressor.unused_data"><code class="xref py py-attr docutils literal notranslate"><span class="pre">unused_data</span></code></a> attribute.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.ZstdDecompressor.eof">
<span class="sig-name descname"><span class="pre">eof</span></span><a class="headerlink" href="#compression.zstd.ZstdDecompressor.eof" title="Link to this definition">¶</a></dt>
<dd><p><code class="docutils literal notranslate"><span class="pre">True</span></code> if the end-of-stream marker has been reached.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.ZstdDecompressor.unused_data">
<span class="sig-name descname"><span class="pre">unused_data</span></span><a class="headerlink" href="#compression.zstd.ZstdDecompressor.unused_data" title="Link to this definition">¶</a></dt>
<dd><p>Data found after the end of the compressed stream.</p>
<p>Before the end of the stream is reached, this will be <code class="docutils literal notranslate"><span class="pre">b''</span></code>.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.ZstdDecompressor.needs_input">
<span class="sig-name descname"><span class="pre">needs_input</span></span><a class="headerlink" href="#compression.zstd.ZstdDecompressor.needs_input" title="Link to this definition">¶</a></dt>
<dd><p><code class="docutils literal notranslate"><span class="pre">False</span></code> if the <a class="reference internal" href="#compression.zstd.ZstdDecompressor.decompress" title="compression.zstd.ZstdDecompressor.decompress"><code class="xref py py-meth docutils literal notranslate"><span class="pre">decompress()</span></code></a> method can provide more
decompressed data before requiring new compressed input.</p>
</dd></dl>

</dd></dl>

</section>
<section id="zstandard-dictionaries">
<h2>Zstandard dictionaries<a class="headerlink" href="#zstandard-dictionaries" title="Link to this heading">¶</a></h2>
<dl class="py function">
<dt class="sig sig-object py" id="compression.zstd.train_dict">
<span class="sig-prename descclassname"><span class="pre">compression.zstd.</span></span><span class="sig-name descname"><span class="pre">train_dict</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">samples</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">dict_size</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#compression.zstd.train_dict" title="Link to this definition">¶</a></dt>
<dd><p>Train a Zstandard dictionary, returning a <a class="reference internal" href="#compression.zstd.ZstdDict" title="compression.zstd.ZstdDict"><code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdDict</span></code></a> instance.
Zstandard dictionaries enable more efficient compression of smaller sizes
of data, which is traditionally difficult to compress due to less
repetition. If you are compressing multiple similar groups of data (such as
similar files), Zstandard dictionaries can improve compression ratios and
speed significantly.</p>
<p>The <em>samples</em> argument (an iterable of <a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> objects), is the
population of samples used to train the Zstandard dictionary.</p>
<p>The <em>dict_size</em> argument, an integer, is the maximum size (in bytes) the
Zstandard dictionary should be. The Zstandard documentation suggests an
absolute maximum of no more than 100 KB, but the maximum can often be smaller
depending on the data. Larger dictionaries generally slow down compression,
but improve compression ratios. Smaller dictionaries lead to faster
compression, but reduce the compression ratio.</p>
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="compression.zstd.finalize_dict">
<span class="sig-prename descclassname"><span class="pre">compression.zstd.</span></span><span class="sig-name descname"><span class="pre">finalize_dict</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">zstd_dict</span></span></em>, <em class="sig-param"><span class="positional-only-separator o"><abbr title="Positional-only parameter separator (PEP 570)"><span class="pre">/</span></abbr></span></em>, <em class="sig-param"><span class="n"><span class="pre">samples</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">dict_size</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">level</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#compression.zstd.finalize_dict" title="Link to this definition">¶</a></dt>
<dd><p>An advanced function for converting a “raw content” Zstandard dictionary into
a regular Zstandard dictionary. “Raw content” dictionaries are a sequence of
bytes that do not need to follow the structure of a normal Zstandard
dictionary.</p>
<p>The <em>zstd_dict</em> argument is a <a class="reference internal" href="#compression.zstd.ZstdDict" title="compression.zstd.ZstdDict"><code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdDict</span></code></a> instance with
the <a class="reference internal" href="#compression.zstd.ZstdDict.dict_content" title="compression.zstd.ZstdDict.dict_content"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dict_content</span></code></a> containing the raw dictionary contents.</p>
<p>The <em>samples</em> argument (an iterable of <a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> objects), contains
sample data for generating the Zstandard dictionary.</p>
<p>The <em>dict_size</em> argument, an integer, is the maximum size (in bytes) the
Zstandard dictionary should be. See <a class="reference internal" href="#compression.zstd.train_dict" title="compression.zstd.train_dict"><code class="xref py py-func docutils literal notranslate"><span class="pre">train_dict()</span></code></a> for
suggestions on the maximum dictionary size.</p>
<p>The <em>level</em> argument (an integer) is the compression level expected to be
passed to the compressors using this dictionary. The dictionary information
varies for each compression level, so tuning for the proper compression
level can make compression more efficient.</p>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="compression.zstd.ZstdDict">
<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">compression.zstd.</span></span><span class="sig-name descname"><span class="pre">ZstdDict</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">dict_content</span></span></em>, <em class="sig-param"><span class="positional-only-separator o"><abbr title="Positional-only parameter separator (PEP 570)"><span class="pre">/</span></abbr></span></em>, <em class="sig-param"><span class="keyword-only-separator o"><abbr title="Keyword-only parameters separator (PEP 3102)"><span class="pre">*</span></abbr></span></em>, <em class="sig-param"><span class="n"><span class="pre">is_raw</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">False</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#compression.zstd.ZstdDict" title="Link to this definition">¶</a></dt>
<dd><p>A wrapper around Zstandard dictionaries. Dictionaries can be used to improve
the compression of many small chunks of data. Use <a class="reference internal" href="#compression.zstd.train_dict" title="compression.zstd.train_dict"><code class="xref py py-func docutils literal notranslate"><span class="pre">train_dict()</span></code></a> if you
need to train a new dictionary from sample data.</p>
<p>The <em>dict_content</em> argument (a <a class="reference internal" href="../glossary.html#term-bytes-like-object"><span class="xref std std-term">bytes-like object</span></a>), is the already
trained dictionary information.</p>
<p>The <em>is_raw</em> argument, a boolean, is an advanced parameter controlling the
meaning of <em>dict_content</em>. <code class="docutils literal notranslate"><span class="pre">True</span></code> means <em>dict_content</em> is a “raw content”
dictionary, without any format restrictions. <code class="docutils literal notranslate"><span class="pre">False</span></code> means <em>dict_content</em>
is an ordinary Zstandard dictionary, created from Zstandard functions,
for example, <a class="reference internal" href="#compression.zstd.train_dict" title="compression.zstd.train_dict"><code class="xref py py-func docutils literal notranslate"><span class="pre">train_dict()</span></code></a> or the external <strong class="program">zstd</strong> CLI.</p>
<p>When passing a <code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdDict</span></code> to a function, the
<code class="xref py py-attr docutils literal notranslate"><span class="pre">as_digested_dict</span></code> and <code class="xref py py-attr docutils literal notranslate"><span class="pre">as_undigested_dict</span></code> attributes can
control how the dictionary is loaded by passing them as the <code class="docutils literal notranslate"><span class="pre">zstd_dict</span></code>
argument, for example, <code class="docutils literal notranslate"><span class="pre">compress(data,</span> <span class="pre">zstd_dict=zd.as_digested_dict)</span></code>.
Digesting a dictionary is a costly operation that occurs when loading a
Zstandard dictionary. When making multiple calls to compression or
decompression, passing a digested dictionary will reduce the overhead of
loading the dictionary.</p>
<blockquote>
<div><table class="docutils align-default" id="id1">
<caption><span class="caption-text">Difference for compression</span><a class="headerlink" href="#id1" title="Link to this table">¶</a></caption>
<colgroup>
<col style="width: 29.4%" />
<col style="width: 41.2%" />
<col style="width: 29.4%" />
</colgroup>
<thead>
<tr class="row-odd"><th class="head"></th>
<th class="head"><p>Digested dictionary</p></th>
<th class="head"><p>Undigested dictionary</p></th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><p>Advanced parameters of the compressor which may be overridden by
the dictionary’s parameters</p></td>
<td><p><code class="docutils literal notranslate"><span class="pre">window_log</span></code>, <code class="docutils literal notranslate"><span class="pre">hash_log</span></code>, <code class="docutils literal notranslate"><span class="pre">chain_log</span></code>, <code class="docutils literal notranslate"><span class="pre">search_log</span></code>,
<code class="docutils literal notranslate"><span class="pre">min_match</span></code>, <code class="docutils literal notranslate"><span class="pre">target_length</span></code>, <code class="docutils literal notranslate"><span class="pre">strategy</span></code>,
<code class="docutils literal notranslate"><span class="pre">enable_long_distance_matching</span></code>, <code class="docutils literal notranslate"><span class="pre">ldm_hash_log</span></code>,
<code class="docutils literal notranslate"><span class="pre">ldm_min_match</span></code>, <code class="docutils literal notranslate"><span class="pre">ldm_bucket_size_log</span></code>, <code class="docutils literal notranslate"><span class="pre">ldm_hash_rate_log</span></code>,
and some non-public parameters.</p></td>
<td><p>None</p></td>
</tr>
<tr class="row-odd"><td><p><code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdDict</span></code> internally caches the dictionary</p></td>
<td><p>Yes. It’s faster when loading a digested dictionary again with the
same compression level.</p></td>
<td><p>No. If you wish to load an undigested dictionary multiple times,
consider reusing a compressor object.</p></td>
</tr>
</tbody>
</table>
</div></blockquote>
<p>If passing a <code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdDict</span></code> without any attribute, an undigested
dictionary is passed by default when compressing and a digested dictionary
is generated if necessary and passed by default when decompressing.</p>
<blockquote>
<div><dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.ZstdDict.dict_content">
<span class="sig-name descname"><span class="pre">dict_content</span></span><a class="headerlink" href="#compression.zstd.ZstdDict.dict_content" title="Link to this definition">¶</a></dt>
<dd><p>The content of the Zstandard dictionary, a <code class="docutils literal notranslate"><span class="pre">bytes</span></code> object. It’s the
same as the <em>dict_content</em> argument in the <code class="docutils literal notranslate"><span class="pre">__init__</span></code> method. It can
be used with other programs, such as the <code class="docutils literal notranslate"><span class="pre">zstd</span></code> CLI program.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.ZstdDict.dict_id">
<span class="sig-name descname"><span class="pre">dict_id</span></span><a class="headerlink" href="#compression.zstd.ZstdDict.dict_id" title="Link to this definition">¶</a></dt>
<dd><p>Identifier of the Zstandard dictionary, a non-negative int value.</p>
<p>Non-zero means the dictionary is ordinary, created by Zstandard
functions and following the Zstandard format.</p>
<p><code class="docutils literal notranslate"><span class="pre">0</span></code> means a “raw content” dictionary, free of any format restriction,
used for advanced users.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>The meaning of <code class="docutils literal notranslate"><span class="pre">0</span></code> for <code class="xref py py-attr docutils literal notranslate"><span class="pre">ZstdDict.dict_id</span></code> is different
from the <code class="docutils literal notranslate"><span class="pre">dictionary_id</span></code> attribute to the <a class="reference internal" href="#compression.zstd.get_frame_info" title="compression.zstd.get_frame_info"><code class="xref py py-func docutils literal notranslate"><span class="pre">get_frame_info()</span></code></a>
function.</p>
</div>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.ZstdDict.as_digested_dict">
<span class="sig-name descname"><span class="pre">as_digested_dict</span></span><a class="headerlink" href="#compression.zstd.ZstdDict.as_digested_dict" title="Link to this definition">¶</a></dt>
<dd><p>Load as a digested dictionary.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.ZstdDict.as_undigested_dict">
<span class="sig-name descname"><span class="pre">as_undigested_dict</span></span><a class="headerlink" href="#compression.zstd.ZstdDict.as_undigested_dict" title="Link to this definition">¶</a></dt>
<dd><p>Load as an undigested dictionary.</p>
</dd></dl>

</div></blockquote>
</dd></dl>

</section>
<section id="advanced-parameter-control">
<h2>Advanced parameter control<a class="headerlink" href="#advanced-parameter-control" title="Link to this heading">¶</a></h2>
<dl class="py class">
<dt class="sig sig-object py" id="compression.zstd.CompressionParameter">
<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">compression.zstd.</span></span><span class="sig-name descname"><span class="pre">CompressionParameter</span></span><a class="headerlink" href="#compression.zstd.CompressionParameter" title="Link to this definition">¶</a></dt>
<dd><p>An <a class="reference internal" href="enum.html#enum.IntEnum" title="enum.IntEnum"><code class="xref py py-class docutils literal notranslate"><span class="pre">IntEnum</span></code></a> containing the advanced compression parameter
keys that can be used when compressing data.</p>
<p>The <a class="reference internal" href="#compression.zstd.CompressionParameter.bounds" title="compression.zstd.CompressionParameter.bounds"><code class="xref py py-meth docutils literal notranslate"><span class="pre">bounds()</span></code></a> method can be used on any attribute to get the valid
values for that parameter.</p>
<p>Parameters are optional; any omitted parameter will have it’s value selected
automatically.</p>
<p>Example getting the lower and upper bound of <a class="reference internal" href="#compression.zstd.CompressionParameter.compression_level" title="compression.zstd.CompressionParameter.compression_level"><code class="xref py py-attr docutils literal notranslate"><span class="pre">compression_level</span></code></a>:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">lower</span><span class="p">,</span> <span class="n">upper</span> <span class="o">=</span> <span class="n">CompressionParameter</span><span class="o">.</span><span class="n">compression_level</span><span class="o">.</span><span class="n">bounds</span><span class="p">()</span>
</pre></div>
</div>
<p>Example setting the <a class="reference internal" href="#compression.zstd.CompressionParameter.window_log" title="compression.zstd.CompressionParameter.window_log"><code class="xref py py-attr docutils literal notranslate"><span class="pre">window_log</span></code></a> to the maximum size:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">_lower</span><span class="p">,</span> <span class="n">upper</span> <span class="o">=</span> <span class="n">CompressionParameter</span><span class="o">.</span><span class="n">window_log</span><span class="o">.</span><span class="n">bounds</span><span class="p">()</span>
<span class="n">options</span> <span class="o">=</span> <span class="p">{</span><span class="n">CompressionParameter</span><span class="o">.</span><span class="n">window_log</span><span class="p">:</span> <span class="n">upper</span><span class="p">}</span>
<span class="n">compress</span><span class="p">(</span><span class="sa">b</span><span class="s1">&#39;venezuelan beaver cheese&#39;</span><span class="p">,</span> <span class="n">options</span><span class="o">=</span><span class="n">options</span><span class="p">)</span>
</pre></div>
</div>
<dl class="py method">
<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.bounds">
<span class="sig-name descname"><span class="pre">bounds</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#compression.zstd.CompressionParameter.bounds" title="Link to this definition">¶</a></dt>
<dd><p>Return the tuple of int bounds, <code class="docutils literal notranslate"><span class="pre">(lower,</span> <span class="pre">upper)</span></code>, of a compression
parameter. This method should be called on the attribute you wish to
retrieve the bounds of. For example, to get the valid values for
<a class="reference internal" href="#compression.zstd.CompressionParameter.compression_level" title="compression.zstd.CompressionParameter.compression_level"><code class="xref py py-attr docutils literal notranslate"><span class="pre">compression_level</span></code></a>, one may check the result of
<code class="docutils literal notranslate"><span class="pre">CompressionParameter.compression_level.bounds()</span></code>.</p>
<p>Both the lower and upper bounds are inclusive.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.compression_level">
<span class="sig-name descname"><span class="pre">compression_level</span></span><a class="headerlink" href="#compression.zstd.CompressionParameter.compression_level" title="Link to this definition">¶</a></dt>
<dd><p>A high-level means of setting other compression parameters that affect
the speed and ratio of compressing data.</p>
<p>Regular compression levels are greater than <code class="docutils literal notranslate"><span class="pre">0</span></code>. Values greater than
<code class="docutils literal notranslate"><span class="pre">20</span></code> are considered “ultra” compression and require more memory than
other levels. Negative values can be used to trade off faster compression
for worse compression ratios.</p>
<p>Setting the level to zero uses <a class="reference internal" href="#compression.zstd.COMPRESSION_LEVEL_DEFAULT" title="compression.zstd.COMPRESSION_LEVEL_DEFAULT"><code class="xref py py-attr docutils literal notranslate"><span class="pre">COMPRESSION_LEVEL_DEFAULT</span></code></a>.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.window_log">
<span class="sig-name descname"><span class="pre">window_log</span></span><a class="headerlink" href="#compression.zstd.CompressionParameter.window_log" title="Link to this definition">¶</a></dt>
<dd><p>Maximum allowed back-reference distance the compressor can use when
compressing data, expressed as power of two, <code class="docutils literal notranslate"><span class="pre">1</span> <span class="pre">&lt;&lt;</span> <span class="pre">window_log</span></code> bytes.
This parameter greatly influences the memory usage of compression. Higher
values require more memory but gain better compression values.</p>
<p>A value of zero causes the value to be selected automatically.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.hash_log">
<span class="sig-name descname"><span class="pre">hash_log</span></span><a class="headerlink" href="#compression.zstd.CompressionParameter.hash_log" title="Link to this definition">¶</a></dt>
<dd><p>Size of the initial probe table, as a power of two. The resulting memory
usage is <code class="docutils literal notranslate"><span class="pre">1</span> <span class="pre">&lt;&lt;</span> <span class="pre">(hash_log+2)</span></code> bytes. Larger tables improve compression
ratio of strategies &lt;= <a class="reference internal" href="#compression.zstd.Strategy.dfast" title="compression.zstd.Strategy.dfast"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dfast</span></code></a>, and improve compression
speed of strategies &gt; <code class="xref py py-attr docutils literal notranslate"><span class="pre">dfast</span></code>.</p>
<p>A value of zero causes the value to be selected automatically.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.chain_log">
<span class="sig-name descname"><span class="pre">chain_log</span></span><a class="headerlink" href="#compression.zstd.CompressionParameter.chain_log" title="Link to this definition">¶</a></dt>
<dd><p>Size of the multi-probe search table, as a power of two. The resulting
memory usage is <code class="docutils literal notranslate"><span class="pre">1</span> <span class="pre">&lt;&lt;</span> <span class="pre">(chain_log+2)</span></code> bytes. Larger tables result in
better and slower compression. This parameter has no effect for the
<a class="reference internal" href="#compression.zstd.Strategy.fast" title="compression.zstd.Strategy.fast"><code class="xref py py-attr docutils literal notranslate"><span class="pre">fast</span></code></a> strategy. It’s still useful when using
<a class="reference internal" href="#compression.zstd.Strategy.dfast" title="compression.zstd.Strategy.dfast"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dfast</span></code></a> strategy, in which case it defines a secondary
probe table.</p>
<p>A value of zero causes the value to be selected automatically.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.search_log">
<span class="sig-name descname"><span class="pre">search_log</span></span><a class="headerlink" href="#compression.zstd.CompressionParameter.search_log" title="Link to this definition">¶</a></dt>
<dd><p>Number of search attempts, as a power of two. More attempts result in
better and slower compression. This parameter is useless for
<a class="reference internal" href="#compression.zstd.Strategy.fast" title="compression.zstd.Strategy.fast"><code class="xref py py-attr docutils literal notranslate"><span class="pre">fast</span></code></a> and <a class="reference internal" href="#compression.zstd.Strategy.dfast" title="compression.zstd.Strategy.dfast"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dfast</span></code></a> strategies.</p>
<p>A value of zero causes the value to be selected automatically.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.min_match">
<span class="sig-name descname"><span class="pre">min_match</span></span><a class="headerlink" href="#compression.zstd.CompressionParameter.min_match" title="Link to this definition">¶</a></dt>
<dd><p>Minimum size of searched matches. Larger values increase compression and
decompression speed, but decrease ratio. Note that Zstandard can still
find matches of smaller size, it just tweaks its search algorithm to look
for this size and larger. For all strategies &lt; <a class="reference internal" href="#compression.zstd.Strategy.btopt" title="compression.zstd.Strategy.btopt"><code class="xref py py-attr docutils literal notranslate"><span class="pre">btopt</span></code></a>,
the effective minimum is <code class="docutils literal notranslate"><span class="pre">4</span></code>; for all strategies
&gt; <a class="reference internal" href="#compression.zstd.Strategy.fast" title="compression.zstd.Strategy.fast"><code class="xref py py-attr docutils literal notranslate"><span class="pre">fast</span></code></a>, the effective maximum is <code class="docutils literal notranslate"><span class="pre">6</span></code>.</p>
<p>A value of zero causes the value to be selected automatically.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.target_length">
<span class="sig-name descname"><span class="pre">target_length</span></span><a class="headerlink" href="#compression.zstd.CompressionParameter.target_length" title="Link to this definition">¶</a></dt>
<dd><p>The impact of this field depends on the selected <a class="reference internal" href="#compression.zstd.Strategy" title="compression.zstd.Strategy"><code class="xref py py-class docutils literal notranslate"><span class="pre">Strategy</span></code></a>.</p>
<p>For strategies <a class="reference internal" href="#compression.zstd.Strategy.btopt" title="compression.zstd.Strategy.btopt"><code class="xref py py-attr docutils literal notranslate"><span class="pre">btopt</span></code></a>, <a class="reference internal" href="#compression.zstd.Strategy.btultra" title="compression.zstd.Strategy.btultra"><code class="xref py py-attr docutils literal notranslate"><span class="pre">btultra</span></code></a> and
<a class="reference internal" href="#compression.zstd.Strategy.btultra2" title="compression.zstd.Strategy.btultra2"><code class="xref py py-attr docutils literal notranslate"><span class="pre">btultra2</span></code></a>, the value is the length of a match
considered “good enough” to stop searching. Larger values make
compression ratios better, but compresses slower.</p>
<p>For strategy <a class="reference internal" href="#compression.zstd.Strategy.fast" title="compression.zstd.Strategy.fast"><code class="xref py py-attr docutils literal notranslate"><span class="pre">fast</span></code></a>, it is the distance between match
sampling. Larger values make compression faster, but with a worse
compression ratio.</p>
<p>A value of zero causes the value to be selected automatically.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.strategy">
<span class="sig-name descname"><span class="pre">strategy</span></span><a class="headerlink" href="#compression.zstd.CompressionParameter.strategy" title="Link to this definition">¶</a></dt>
<dd><p>The higher the value of selected strategy, the more complex the
compression technique used by zstd, resulting in higher compression
ratios but slower compression.</p>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<p><a class="reference internal" href="#compression.zstd.Strategy" title="compression.zstd.Strategy"><code class="xref py py-class docutils literal notranslate"><span class="pre">Strategy</span></code></a></p>
</div>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.enable_long_distance_matching">
<span class="sig-name descname"><span class="pre">enable_long_distance_matching</span></span><a class="headerlink" href="#compression.zstd.CompressionParameter.enable_long_distance_matching" title="Link to this definition">¶</a></dt>
<dd><p>Long distance matching can be used to improve compression for large
inputs by finding large matches at greater distances. It increases memory
usage and window size.</p>
<p><code class="docutils literal notranslate"><span class="pre">True</span></code> or <code class="docutils literal notranslate"><span class="pre">1</span></code> enable long distance matching while <code class="docutils literal notranslate"><span class="pre">False</span></code> or <code class="docutils literal notranslate"><span class="pre">0</span></code>
disable it.</p>
<p>Enabling this parameter increases default
<a class="reference internal" href="#compression.zstd.CompressionParameter.window_log" title="compression.zstd.CompressionParameter.window_log"><code class="xref py py-attr docutils literal notranslate"><span class="pre">window_log</span></code></a> to 128 MiB except when expressly
set to a different value. This setting is enabled by default if
<code class="xref py py-attr docutils literal notranslate"><span class="pre">window_log</span></code> &gt;= 128 MiB and the compression
strategy &gt;= <a class="reference internal" href="#compression.zstd.Strategy.btopt" title="compression.zstd.Strategy.btopt"><code class="xref py py-attr docutils literal notranslate"><span class="pre">btopt</span></code></a> (compression level 16+).</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.ldm_hash_log">
<span class="sig-name descname"><span class="pre">ldm_hash_log</span></span><a class="headerlink" href="#compression.zstd.CompressionParameter.ldm_hash_log" title="Link to this definition">¶</a></dt>
<dd><p>Size of the table for long distance matching, as a power of two. Larger
values increase memory usage and compression ratio, but decrease
compression speed.</p>
<p>A value of zero causes the value to be selected automatically.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.ldm_min_match">
<span class="sig-name descname"><span class="pre">ldm_min_match</span></span><a class="headerlink" href="#compression.zstd.CompressionParameter.ldm_min_match" title="Link to this definition">¶</a></dt>
<dd><p>Minimum match size for long distance matcher. Larger or too small values
can often decrease the compression ratio.</p>
<p>A value of zero causes the value to be selected automatically.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.ldm_bucket_size_log">
<span class="sig-name descname"><span class="pre">ldm_bucket_size_log</span></span><a class="headerlink" href="#compression.zstd.CompressionParameter.ldm_bucket_size_log" title="Link to this definition">¶</a></dt>
<dd><p>Log size of each bucket in the long distance matcher hash table for
collision resolution. Larger values improve collision resolution but
decrease compression speed.</p>
<p>A value of zero causes the value to be selected automatically.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.ldm_hash_rate_log">
<span class="sig-name descname"><span class="pre">ldm_hash_rate_log</span></span><a class="headerlink" href="#compression.zstd.CompressionParameter.ldm_hash_rate_log" title="Link to this definition">¶</a></dt>
<dd><p>Frequency of inserting/looking up entries into the long distance matcher
hash table. Larger values improve compression speed. Deviating far from
the default value will likely result in a compression ratio decrease.</p>
<p>A value of zero causes the value to be selected automatically.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.content_size_flag">
<span class="sig-name descname"><span class="pre">content_size_flag</span></span><a class="headerlink" href="#compression.zstd.CompressionParameter.content_size_flag" title="Link to this definition">¶</a></dt>
<dd><p>Write the size of the data to be compressed into the Zstandard frame
header when known prior to compressing.</p>
<p>This flag only takes effect under the following scenarios:</p>
<ul class="simple">
<li><p>Calling <a class="reference internal" href="#compression.zstd.compress" title="compression.zstd.compress"><code class="xref py py-func docutils literal notranslate"><span class="pre">compress()</span></code></a> for one-shot compression</p></li>
<li><p>Providing all of the data to be compressed in the frame in a single
<a class="reference internal" href="#compression.zstd.ZstdCompressor.compress" title="compression.zstd.ZstdCompressor.compress"><code class="xref py py-meth docutils literal notranslate"><span class="pre">ZstdCompressor.compress()</span></code></a> call, with the
<a class="reference internal" href="#compression.zstd.ZstdCompressor.FLUSH_FRAME" title="compression.zstd.ZstdCompressor.FLUSH_FRAME"><code class="xref py py-attr docutils literal notranslate"><span class="pre">ZstdCompressor.FLUSH_FRAME</span></code></a> mode.</p></li>
<li><p>Calling <a class="reference internal" href="#compression.zstd.ZstdCompressor.set_pledged_input_size" title="compression.zstd.ZstdCompressor.set_pledged_input_size"><code class="xref py py-meth docutils literal notranslate"><span class="pre">ZstdCompressor.set_pledged_input_size()</span></code></a> with the exact
amount of data that will be provided to the compressor prior to any
calls to <a class="reference internal" href="#compression.zstd.ZstdCompressor.compress" title="compression.zstd.ZstdCompressor.compress"><code class="xref py py-meth docutils literal notranslate"><span class="pre">ZstdCompressor.compress()</span></code></a> for the current frame.
<code class="xref py py-meth docutils literal notranslate"><span class="pre">ZstdCompressor.set_pledged_input_size()</span></code> must be called for each
new frame.</p></li>
</ul>
<p>All other compression calls may not write the size information into the
frame header.</p>
<p><code class="docutils literal notranslate"><span class="pre">True</span></code> or <code class="docutils literal notranslate"><span class="pre">1</span></code> enable the content size flag while <code class="docutils literal notranslate"><span class="pre">False</span></code> or <code class="docutils literal notranslate"><span class="pre">0</span></code>
disable it.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.checksum_flag">
<span class="sig-name descname"><span class="pre">checksum_flag</span></span><a class="headerlink" href="#compression.zstd.CompressionParameter.checksum_flag" title="Link to this definition">¶</a></dt>
<dd><p>A four-byte checksum using XXHash64 of the uncompressed content is
written at the end of each frame. Zstandard’s decompression code verifies
the checksum. If there is a mismatch a <a class="reference internal" href="#compression.zstd.ZstdError" title="compression.zstd.ZstdError"><code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdError</span></code></a> exception is
raised.</p>
<p><code class="docutils literal notranslate"><span class="pre">True</span></code> or <code class="docutils literal notranslate"><span class="pre">1</span></code> enable checksum generation while <code class="docutils literal notranslate"><span class="pre">False</span></code> or <code class="docutils literal notranslate"><span class="pre">0</span></code>
disable it.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.dict_id_flag">
<span class="sig-name descname"><span class="pre">dict_id_flag</span></span><a class="headerlink" href="#compression.zstd.CompressionParameter.dict_id_flag" title="Link to this definition">¶</a></dt>
<dd><p>When compressing with a <a class="reference internal" href="#compression.zstd.ZstdDict" title="compression.zstd.ZstdDict"><code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdDict</span></code></a>, the dictionary’s ID is written
into the frame header.</p>
<p><code class="docutils literal notranslate"><span class="pre">True</span></code> or <code class="docutils literal notranslate"><span class="pre">1</span></code> enable storing the dictionary ID while <code class="docutils literal notranslate"><span class="pre">False</span></code> or
<code class="docutils literal notranslate"><span class="pre">0</span></code> disable it.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.nb_workers">
<span class="sig-name descname"><span class="pre">nb_workers</span></span><a class="headerlink" href="#compression.zstd.CompressionParameter.nb_workers" title="Link to this definition">¶</a></dt>
<dd><p>Select how many threads will be spawned to compress in parallel. When
<code class="xref py py-attr docutils literal notranslate"><span class="pre">nb_workers</span></code> &gt; 0, enables multi-threaded compression, a value of
<code class="docutils literal notranslate"><span class="pre">1</span></code> means “one-thread multi-threaded mode”. More workers improve speed,
but also increase memory usage and slightly reduce compression ratio.</p>
<p>A value of zero disables multi-threading.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.job_size">
<span class="sig-name descname"><span class="pre">job_size</span></span><a class="headerlink" href="#compression.zstd.CompressionParameter.job_size" title="Link to this definition">¶</a></dt>
<dd><p>Size of a compression job, in bytes. This value is enforced only when
<a class="reference internal" href="#compression.zstd.CompressionParameter.nb_workers" title="compression.zstd.CompressionParameter.nb_workers"><code class="xref py py-attr docutils literal notranslate"><span class="pre">nb_workers</span></code></a> &gt;= 1. Each compression job is
completed in parallel, so this value can indirectly impact the number of
active threads.</p>
<p>A value of zero causes the value to be selected automatically.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.overlap_log">
<span class="sig-name descname"><span class="pre">overlap_log</span></span><a class="headerlink" href="#compression.zstd.CompressionParameter.overlap_log" title="Link to this definition">¶</a></dt>
<dd><p>Sets how much data is reloaded from previous jobs (threads) for new jobs
to be used by the look behind window during compression. This value is
only used when <a class="reference internal" href="#compression.zstd.CompressionParameter.nb_workers" title="compression.zstd.CompressionParameter.nb_workers"><code class="xref py py-attr docutils literal notranslate"><span class="pre">nb_workers</span></code></a> &gt;= 1. Acceptable
values vary from 0 to 9.</p>
<blockquote>
<div><ul class="simple">
<li><p>0 means dynamically set the overlap amount</p></li>
<li><p>1 means no overlap</p></li>
<li><p>9 means use a full window size from the previous job</p></li>
</ul>
</div></blockquote>
<p>Each increment halves/doubles the overlap size. “8” means an overlap of
<code class="docutils literal notranslate"><span class="pre">window_size/2</span></code>, “7” means an overlap of <code class="docutils literal notranslate"><span class="pre">window_size/4</span></code>, etc.</p>
</dd></dl>

</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="compression.zstd.DecompressionParameter">
<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">compression.zstd.</span></span><span class="sig-name descname"><span class="pre">DecompressionParameter</span></span><a class="headerlink" href="#compression.zstd.DecompressionParameter" title="Link to this definition">¶</a></dt>
<dd><p>An <a class="reference internal" href="enum.html#enum.IntEnum" title="enum.IntEnum"><code class="xref py py-class docutils literal notranslate"><span class="pre">IntEnum</span></code></a> containing the advanced decompression parameter
keys that can be used when decompressing data. Parameters are optional; any
omitted parameter will have it’s value selected automatically.</p>
<p>The <a class="reference internal" href="#compression.zstd.DecompressionParameter.bounds" title="compression.zstd.DecompressionParameter.bounds"><code class="xref py py-meth docutils literal notranslate"><span class="pre">bounds()</span></code></a> method can be used on any attribute to get the valid
values for that parameter.</p>
<p>Example setting the <a class="reference internal" href="#compression.zstd.DecompressionParameter.window_log_max" title="compression.zstd.DecompressionParameter.window_log_max"><code class="xref py py-attr docutils literal notranslate"><span class="pre">window_log_max</span></code></a> to the maximum size:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">data</span> <span class="o">=</span> <span class="n">compress</span><span class="p">(</span><span class="sa">b</span><span class="s1">&#39;Some very long buffer of bytes...&#39;</span><span class="p">)</span>

<span class="n">_lower</span><span class="p">,</span> <span class="n">upper</span> <span class="o">=</span> <span class="n">DecompressionParameter</span><span class="o">.</span><span class="n">window_log_max</span><span class="o">.</span><span class="n">bounds</span><span class="p">()</span>

<span class="n">options</span> <span class="o">=</span> <span class="p">{</span><span class="n">DecompressionParameter</span><span class="o">.</span><span class="n">window_log_max</span><span class="p">:</span> <span class="n">upper</span><span class="p">}</span>
<span class="n">decompress</span><span class="p">(</span><span class="n">data</span><span class="p">,</span> <span class="n">options</span><span class="o">=</span><span class="n">options</span><span class="p">)</span>
</pre></div>
</div>
<dl class="py method">
<dt class="sig sig-object py" id="compression.zstd.DecompressionParameter.bounds">
<span class="sig-name descname"><span class="pre">bounds</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#compression.zstd.DecompressionParameter.bounds" title="Link to this definition">¶</a></dt>
<dd><p>Return the tuple of int bounds, <code class="docutils literal notranslate"><span class="pre">(lower,</span> <span class="pre">upper)</span></code>, of a decompression
parameter. This method should be called on the attribute you wish to
retrieve the bounds of.</p>
<p>Both the lower and upper bounds are inclusive.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.DecompressionParameter.window_log_max">
<span class="sig-name descname"><span class="pre">window_log_max</span></span><a class="headerlink" href="#compression.zstd.DecompressionParameter.window_log_max" title="Link to this definition">¶</a></dt>
<dd><p>The base-two logarithm of the maximum size of the window used during
decompression. This can be useful to limit the amount of memory used when
decompressing data. A larger maximum window size leads to faster
decompression.</p>
<p>A value of zero causes the value to be selected automatically.</p>
</dd></dl>

</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="compression.zstd.Strategy">
<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">compression.zstd.</span></span><span class="sig-name descname"><span class="pre">Strategy</span></span><a class="headerlink" href="#compression.zstd.Strategy" title="Link to this definition">¶</a></dt>
<dd><p>An <a class="reference internal" href="enum.html#enum.IntEnum" title="enum.IntEnum"><code class="xref py py-class docutils literal notranslate"><span class="pre">IntEnum</span></code></a> containing strategies for compression.
Higher-numbered strategies correspond to more complex and slower
compression.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>The values of attributes of <code class="xref py py-class docutils literal notranslate"><span class="pre">Strategy</span></code> are not necessarily stable
across zstd versions. Only the ordering of the attributes may be relied
upon. The attributes are listed below in order.</p>
</div>
<p>The following strategies are available:</p>
<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.Strategy.fast">
<span class="sig-name descname"><span class="pre">fast</span></span><a class="headerlink" href="#compression.zstd.Strategy.fast" title="Link to this definition">¶</a></dt>
<dd></dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.Strategy.dfast">
<span class="sig-name descname"><span class="pre">dfast</span></span><a class="headerlink" href="#compression.zstd.Strategy.dfast" title="Link to this definition">¶</a></dt>
<dd></dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.Strategy.greedy">
<span class="sig-name descname"><span class="pre">greedy</span></span><a class="headerlink" href="#compression.zstd.Strategy.greedy" title="Link to this definition">¶</a></dt>
<dd></dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.Strategy.lazy">
<span class="sig-name descname"><span class="pre">lazy</span></span><a class="headerlink" href="#compression.zstd.Strategy.lazy" title="Link to this definition">¶</a></dt>
<dd></dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.Strategy.lazy2">
<span class="sig-name descname"><span class="pre">lazy2</span></span><a class="headerlink" href="#compression.zstd.Strategy.lazy2" title="Link to this definition">¶</a></dt>
<dd></dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.Strategy.btlazy2">
<span class="sig-name descname"><span class="pre">btlazy2</span></span><a class="headerlink" href="#compression.zstd.Strategy.btlazy2" title="Link to this definition">¶</a></dt>
<dd></dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.Strategy.btopt">
<span class="sig-name descname"><span class="pre">btopt</span></span><a class="headerlink" href="#compression.zstd.Strategy.btopt" title="Link to this definition">¶</a></dt>
<dd></dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.Strategy.btultra">
<span class="sig-name descname"><span class="pre">btultra</span></span><a class="headerlink" href="#compression.zstd.Strategy.btultra" title="Link to this definition">¶</a></dt>
<dd></dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.Strategy.btultra2">
<span class="sig-name descname"><span class="pre">btultra2</span></span><a class="headerlink" href="#compression.zstd.Strategy.btultra2" title="Link to this definition">¶</a></dt>
<dd></dd></dl>

</dd></dl>

</section>
<section id="miscellaneous">
<h2>Miscellaneous<a class="headerlink" href="#miscellaneous" title="Link to this heading">¶</a></h2>
<dl class="py function">
<dt class="sig sig-object py" id="compression.zstd.get_frame_info">
<span class="sig-prename descclassname"><span class="pre">compression.zstd.</span></span><span class="sig-name descname"><span class="pre">get_frame_info</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">frame_buffer</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#compression.zstd.get_frame_info" title="Link to this definition">¶</a></dt>
<dd><p>Retrieve a <a class="reference internal" href="#compression.zstd.FrameInfo" title="compression.zstd.FrameInfo"><code class="xref py py-class docutils literal notranslate"><span class="pre">FrameInfo</span></code></a> object containing metadata about a Zstandard
frame. Frames contain metadata related to the compressed data they hold.</p>
</dd></dl>

<dl class="py class">
<dt class="sig sig-object py" id="compression.zstd.FrameInfo">
<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">compression.zstd.</span></span><span class="sig-name descname"><span class="pre">FrameInfo</span></span><a class="headerlink" href="#compression.zstd.FrameInfo" title="Link to this definition">¶</a></dt>
<dd><p>Metadata related to a Zstandard frame.</p>
<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.FrameInfo.decompressed_size">
<span class="sig-name descname"><span class="pre">decompressed_size</span></span><a class="headerlink" href="#compression.zstd.FrameInfo.decompressed_size" title="Link to this definition">¶</a></dt>
<dd><p>The size of the decompressed contents of the frame.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.FrameInfo.dictionary_id">
<span class="sig-name descname"><span class="pre">dictionary_id</span></span><a class="headerlink" href="#compression.zstd.FrameInfo.dictionary_id" title="Link to this definition">¶</a></dt>
<dd><p>An integer representing the Zstandard dictionary ID needed for
decompressing the frame. <code class="docutils literal notranslate"><span class="pre">0</span></code> means the dictionary ID was not
recorded in the frame header. This may mean that a Zstandard dictionary
is not needed, or that the ID of a required dictionary was not recorded.</p>
</dd></dl>

</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.COMPRESSION_LEVEL_DEFAULT">
<span class="sig-prename descclassname"><span class="pre">compression.zstd.</span></span><span class="sig-name descname"><span class="pre">COMPRESSION_LEVEL_DEFAULT</span></span><a class="headerlink" href="#compression.zstd.COMPRESSION_LEVEL_DEFAULT" title="Link to this definition">¶</a></dt>
<dd><p>The default compression level for Zstandard: <code class="docutils literal notranslate"><span class="pre">3</span></code>.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="compression.zstd.zstd_version_info">
<span class="sig-prename descclassname"><span class="pre">compression.zstd.</span></span><span class="sig-name descname"><span class="pre">zstd_version_info</span></span><a class="headerlink" href="#compression.zstd.zstd_version_info" title="Link to this definition">¶</a></dt>
<dd><p>Version number of the runtime zstd library as a tuple of integers
(major, minor, release).</p>
</dd></dl>

</section>
<section id="examples">
<h2>Examples<a class="headerlink" href="#examples" title="Link to this heading">¶</a></h2>
<p>Reading in a compressed file:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span><span class="w"> </span><span class="nn">compression</span><span class="w"> </span><span class="kn">import</span> <span class="n">zstd</span>

<span class="k">with</span> <span class="n">zstd</span><span class="o">.</span><span class="n">open</span><span class="p">(</span><span class="s2">&quot;file.zst&quot;</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>Creating a compressed file:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span><span class="w"> </span><span class="nn">compression</span><span class="w"> </span><span class="kn">import</span> <span class="n">zstd</span>

<span class="n">data</span> <span class="o">=</span> <span class="sa">b</span><span class="s2">&quot;Insert Data Here&quot;</span>
<span class="k">with</span> <span class="n">zstd</span><span class="o">.</span><span class="n">open</span><span class="p">(</span><span class="s2">&quot;file.zst&quot;</span><span class="p">,</span> <span class="s2">&quot;w&quot;</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">data</span><span class="p">)</span>
</pre></div>
</div>
<p>Compressing data in memory:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span><span class="w"> </span><span class="nn">compression</span><span class="w"> </span><span class="kn">import</span> <span class="n">zstd</span>

<span class="n">data_in</span> <span class="o">=</span> <span class="sa">b</span><span class="s2">&quot;Insert Data Here&quot;</span>
<span class="n">data_out</span> <span class="o">=</span> <span class="n">zstd</span><span class="o">.</span><span class="n">compress</span><span class="p">(</span><span class="n">data_in</span><span class="p">)</span>
</pre></div>
</div>
<p>Incremental compression:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span><span class="w"> </span><span class="nn">compression</span><span class="w"> </span><span class="kn">import</span> <span class="n">zstd</span>

<span class="n">comp</span> <span class="o">=</span> <span class="n">zstd</span><span class="o">.</span><span class="n">ZstdCompressor</span><span class="p">()</span>
<span class="n">out1</span> <span class="o">=</span> <span class="n">comp</span><span class="o">.</span><span class="n">compress</span><span class="p">(</span><span class="sa">b</span><span class="s2">&quot;Some data</span><span class="se">\n</span><span class="s2">&quot;</span><span class="p">)</span>
<span class="n">out2</span> <span class="o">=</span> <span class="n">comp</span><span class="o">.</span><span class="n">compress</span><span class="p">(</span><span class="sa">b</span><span class="s2">&quot;Another piece of data</span><span class="se">\n</span><span class="s2">&quot;</span><span class="p">)</span>
<span class="n">out3</span> <span class="o">=</span> <span class="n">comp</span><span class="o">.</span><span class="n">compress</span><span class="p">(</span><span class="sa">b</span><span class="s2">&quot;Even more data</span><span class="se">\n</span><span class="s2">&quot;</span><span class="p">)</span>
<span class="n">out4</span> <span class="o">=</span> <span class="n">comp</span><span class="o">.</span><span class="n">flush</span><span class="p">()</span>
<span class="c1"># Concatenate all the partial results:</span>
<span class="n">result</span> <span class="o">=</span> <span class="sa">b</span><span class="s2">&quot;&quot;</span><span class="o">.</span><span class="n">join</span><span class="p">([</span><span class="n">out1</span><span class="p">,</span> <span class="n">out2</span><span class="p">,</span> <span class="n">out3</span><span class="p">,</span> <span class="n">out4</span><span class="p">])</span>
</pre></div>
</div>
<p>Writing compressed data to an already-open file:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span><span class="w"> </span><span class="nn">compression</span><span class="w"> </span><span class="kn">import</span> <span class="n">zstd</span>

<span class="k">with</span> <span class="nb">open</span><span class="p">(</span><span class="s2">&quot;myfile&quot;</span><span class="p">,</span> <span class="s2">&quot;wb&quot;</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="sa">b</span><span class="s2">&quot;This data will not be compressed</span><span class="se">\n</span><span class="s2">&quot;</span><span class="p">)</span>
    <span class="k">with</span> <span class="n">zstd</span><span class="o">.</span><span class="n">open</span><span class="p">(</span><span class="n">f</span><span class="p">,</span> <span class="s2">&quot;w&quot;</span><span class="p">)</span> <span class="k">as</span> <span class="n">zstf</span><span class="p">:</span>
        <span class="n">zstf</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="sa">b</span><span class="s2">&quot;This *will* be compressed</span><span class="se">\n</span><span class="s2">&quot;</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="sa">b</span><span class="s2">&quot;Not compressed</span><span class="se">\n</span><span class="s2">&quot;</span><span class="p">)</span>
</pre></div>
</div>
<p>Creating a compressed file using compression parameters:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span><span class="w"> </span><span class="nn">compression</span><span class="w"> </span><span class="kn">import</span> <span class="n">zstd</span>

<span class="n">options</span> <span class="o">=</span> <span class="p">{</span>
   <span class="n">zstd</span><span class="o">.</span><span class="n">CompressionParameter</span><span class="o">.</span><span class="n">checksum_flag</span><span class="p">:</span> <span class="mi">1</span>
<span class="p">}</span>
<span class="k">with</span> <span class="n">zstd</span><span class="o">.</span><span class="n">open</span><span class="p">(</span><span class="s2">&quot;file.zst&quot;</span><span class="p">,</span> <span class="s2">&quot;w&quot;</span><span class="p">,</span> <span class="n">options</span><span class="o">=</span><span class="n">options</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="sa">b</span><span class="s2">&quot;Mind if I squeeze in?&quot;</span><span class="p">)</span>
</pre></div>
</div>
</section>
</section>


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    <ul>
<li><a class="reference internal" href="#"><code class="xref py py-mod docutils literal notranslate"><span class="pre">compression.zstd</span></code> — Compression compatible with the Zstandard format</a><ul>
<li><a class="reference internal" href="#exceptions">Exceptions</a></li>
<li><a class="reference internal" href="#reading-and-writing-compressed-files">Reading and writing compressed files</a></li>
<li><a class="reference internal" href="#compressing-and-decompressing-data-in-memory">Compressing and decompressing data in memory</a></li>
<li><a class="reference internal" href="#zstandard-dictionaries">Zstandard dictionaries</a></li>
<li><a class="reference internal" href="#advanced-parameter-control">Advanced parameter control</a></li>
<li><a class="reference internal" href="#miscellaneous">Miscellaneous</a></li>
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