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href="#examples">Examples</a></li>115</ul>116</li>117</ul>118 119  </div>120  <div>121    <h4>Previous topic</h4>122    <p class="topless"><a href="compression.html"123                          title="previous chapter">The <code class="xref py py-mod docutils literal notranslate"><span class="pre">compression</span></code> package</a></p>124  </div>125  <div>126    <h4>Next topic</h4>127    <p class="topless"><a href="zlib.html"128                          title="next chapter"><code class="xref py py-mod docutils literal notranslate"><span class="pre">zlib</span></code> — Compression compatible with <strong class="program">gzip</strong></a></p>129  </div>130  <script>131    document.addEventListener('DOMContentLoaded', () => {132        const title = document.querySelector('meta[property="og:title"]').content;133        const elements = document.querySelectorAll('.improvepage');134        const pageurl = window.location.href.split('?')[0];135        elements.forEach(element => {136     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       |204                </li>205            <li class="right">206<label class="theme-selector-label">207    Theme208    <select class="theme-selector" oninput="activateTheme(this.value)">209        <option value="auto" selected>Auto</option>210        <option value="light">Light</option>211        <option value="dark">Dark</option>212    </select>213</label> |</li>214            215      </ul>216    </div>    217 218    <div class="document">219      <div class="documentwrapper">220        <div class="bodywrapper">221          <div class="body" role="main">222            223  <section id="module-compression.zstd">224<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>225<div class="versionadded">226<p><span class="versionmodified added">Added in version 3.14.</span></p>227</div>228<p><strong>Source code:</strong> <a class="extlink-source reference external" href="https://github.com/python/cpython/tree/main/Lib/compression/zstd/__init__.py">Lib/compression/zstd/__init__.py</a></p>229<hr class="docutils" />230<p>This module provides classes and functions for compressing and decompressing231data using the Zstandard (or <em>zstd</em>) compression algorithm. The232<a class="reference external" href="https://facebook.github.io/zstd/doc/api_manual_latest.html">zstd manual</a>233describes Zstandard as “a fast lossless compression algorithm, targeting234real-time compression scenarios at zlib-level and better compression ratios.”235Also included is a file interface that supports reading and writing the236contents of <code class="docutils literal notranslate"><span class="pre">.zst</span></code> files created by the <strong class="program">zstd</strong> utility, as well as237raw zstd compressed streams.</p>238<p>The <code class="xref py py-mod docutils literal notranslate"><span class="pre">compression.zstd</span></code> module contains:</p>239<ul class="simple">240<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 and241writing compressed files.</p></li>242<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 for243incremental (de)compression.</p></li>244<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-shot245(de)compression.</p></li>246<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 the247<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>248<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>, and249<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>250</ul>251<p>This is an <a class="reference internal" href="../glossary.html#term-optional-module"><span class="xref std std-term">optional module</span></a>.252If it is missing from your copy of CPython,253look for documentation from your distributor (that is,254whoever provided Python to you).255If 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>256<section id="exceptions">257<h2>Exceptions<a class="headerlink" href="#exceptions" title="Link to this heading">¶</a></h2>258<dl class="py exception">259<dt class="sig sig-object py" id="compression.zstd.ZstdError">260<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>261<dd><p>This exception is raised when an error occurs during compression or262decompression, or while initializing the (de)compressor state.</p>263</dd></dl>264 265</section>266<section id="reading-and-writing-compressed-files">267<h2>Reading and writing compressed files<a class="headerlink" href="#reading-and-writing-compressed-files" title="Link to this heading">¶</a></h2>268<dl class="py function">269<dt class="sig sig-object py" id="compression.zstd.open">270<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>271<dd><p>Open a Zstandard-compressed file in binary or text mode, returning a272<a class="reference internal" href="../glossary.html#term-file-object"><span class="xref std std-term">file object</span></a>.</p>273<p>The <em>file</em> argument can be either a file name (given as a274<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>275object), in which case the named file is opened, or it can be an existing276file object to read from or write to.</p>277<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> for278overwriting, <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.279These 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>280respectively. 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>,281<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>282<p>When reading, the <em>options</em> argument can be a dictionary providing advanced283decompression 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 detailed284information about supported285parameters. 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 be286used during decompression. When reading, if the <em>level</em>287argument is not None, a <code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code> will be raised.</p>288<p>When writing, the <em>options</em> argument can be a dictionary289providing advanced compression parameters; see290<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 supported291parameters. The <em>level</em> argument is the compression level to use when292writing compressed data. Only one of <em>level</em> or <em>options</em> may be non-None.293The <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 during294compression.</p>295<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>296constructor: <code class="docutils literal notranslate"><span class="pre">ZstdFile(file,</span> <span class="pre">mode,</span> <span class="pre">...)</span></code>. In this case, the297<em>encoding</em>, <em>errors</em>, and <em>newline</em> parameters must not be provided.</p>298<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 an299<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, error300handling behavior, and line endings.</p>301</dd></dl>302 303<dl class="py class">304<dt class="sig sig-object py" id="compression.zstd.ZstdFile">305<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>306<dd><p>Open a Zstandard-compressed file in binary mode.</p>307<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 operate308directly on a named file. The <em>file</em> argument specifies either the file309object 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>,310<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). If311wrapping an existing file object, the wrapped file will not be closed when312the <code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdFile</span></code> is closed.</p>313<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>314for 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.315These 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>316respectively.</p>317<p>If <em>file</em> is a file object (rather than an actual file name), a mode of318<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>319<p>When reading, the <em>options</em> argument can be a dictionary320providing advanced decompression parameters; see321<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 supported322parameters. 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 be323used during decompression. When reading, if the <em>level</em>324argument is not None, a <code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code> will be raised.</p>325<p>When writing, the <em>options</em> argument can be a dictionary326providing advanced compression parameters; see327<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 supported328parameters. The <em>level</em> argument is the compression level to use when329writing compressed data. Only one of <em>level</em> or <em>options</em> may be passed. The330<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 during331compression.</p>332<p><code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdFile</span></code> supports all the members specified by333<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>334and <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>.335Iteration 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>336<p>The following method and attributes are also provided:</p>337<dl class="py method">338<dt class="sig sig-object py" id="compression.zstd.ZstdFile.peek">339<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>340<dd><p>Return buffered data without advancing the file position. At least one341byte of data will be returned, unless EOF has been reached. The exact342number of bytes returned is unspecified (the <em>size</em> argument is ignored).</p>343<div class="admonition note">344<p class="admonition-title">Note</p>345<p>While calling <code class="xref py py-meth docutils literal notranslate"><span class="pre">peek()</span></code> does not change the file position of346the <code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdFile</span></code>, it may change the position of the underlying347file object (for example, if the <code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdFile</span></code> was constructed by348passing a file object for <em>file</em>).</p>349</div>350</dd></dl>351 352<dl class="py attribute">353<dt class="sig sig-object py" id="compression.zstd.ZstdFile.mode">354<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>355<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>356</dd></dl>357 358<dl class="py attribute">359<dt class="sig sig-object py" id="compression.zstd.ZstdFile.name">360<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>361<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>362attribute of the underlying <a class="reference internal" href="../glossary.html#term-file-object"><span class="xref std std-term">file object</span></a>.</p>363</dd></dl>364 365</dd></dl>366 367</section>368<section id="compressing-and-decompressing-data-in-memory">369<h2>Compressing and decompressing data in memory<a class="headerlink" href="#compressing-and-decompressing-data-in-memory" title="Link to this heading">¶</a></h2>370<dl class="py function">371<dt class="sig sig-object py" id="compression.zstd.compress">372<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>373<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 compressed374data 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>375<p>The <em>level</em> argument is an integer controlling the level of376compression. <em>level</em> is an alternative to setting377<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>. Use378<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> on379<code class="xref py py-attr docutils literal notranslate"><span class="pre">compression_level</span></code> to get the values that can380be passed for <em>level</em>. If advanced compression options are needed, the381<em>level</em> argument must be omitted and in the <em>options</em> dictionary the382<code class="xref py py-attr docutils literal notranslate"><span class="pre">CompressionParameter.compression_level</span></code> parameter should be set.</p>383<p>The <em>options</em> argument is a Python dictionary containing advanced384compression parameters. The valid keys and values for compression parameters385are 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>386<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>387containing trained data to improve compression efficiency. The388function <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>389</dd></dl>390 391<dl class="py function">392<dt class="sig sig-object py" id="compression.zstd.decompress">393<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>394<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 uncompressed395data 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>396<p>The <em>options</em> argument is a Python dictionary containing advanced397decompression parameters. The valid keys and values for compression398parameters 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>399documentation.</p>400<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>401containing trained data used during compression. This must be402the same Zstandard dictionary used during compression.</p>403<p>If <em>data</em> is the concatenation of multiple distinct compressed frames,404decompress all of these frames, and return the concatenation of the results.</p>405</dd></dl>406 407<dl class="py class">408<dt class="sig sig-object py" id="compression.zstd.ZstdCompressor">409<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>410<dd><p>Create a compressor object, which can be used to compress data411incrementally.</p>412<p>For a more convenient way of compressing a single chunk of data, see the413module-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>414<p>The <em>level</em> argument is an integer controlling the level of415compression. <em>level</em> is an alternative to setting416<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>. Use417<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> on418<code class="xref py py-attr docutils literal notranslate"><span class="pre">compression_level</span></code> to get the values that can419be passed for <em>level</em>. If advanced compression options are needed, the420<em>level</em> argument must be omitted and in the <em>options</em> dictionary the421<code class="xref py py-attr docutils literal notranslate"><span class="pre">CompressionParameter.compression_level</span></code> parameter should be set.</p>422<p>The <em>options</em> argument is a Python dictionary containing advanced423compression parameters. The valid keys and values for compression parameters424are 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>425<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>426containing trained data to improve compression efficiency. The427function <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>428<dl class="py method">429<dt class="sig sig-object py" id="compression.zstd.ZstdCompressor.compress">430<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>431<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>432object with compressed data if possible, or otherwise an empty433<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, for434use 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 returned435data should be concatenated with the output of any previous calls to436<code class="xref py py-meth docutils literal notranslate"><span class="pre">compress()</span></code>.</p>437<p>The <em>mode</em> argument is a <code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdCompressor</span></code> attribute, either438<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>,439or <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>440<p>When all data has been provided to the compressor, call the441<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. If442<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>,443<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 empty444frame.</p>445</dd></dl>446 447<dl class="py method">448<dt class="sig sig-object py" id="compression.zstd.ZstdCompressor.flush">449<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>450<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> object451containing any data stored in the compressor’s internal buffers.</p>452<p>The <em>mode</em> argument is a <code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdCompressor</span></code> attribute, either453<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>454</dd></dl>455 456<dl class="py method">457<dt class="sig sig-object py" id="compression.zstd.ZstdCompressor.set_pledged_input_size">458<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>459<dd><p>Specify the amount of uncompressed data <em>size</em> that will be provided for460the next frame. <em>size</em> will be written into the frame header of the next461frame 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>462or <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> is463<code class="docutils literal notranslate"><span class="pre">None</span></code>, the frame header will omit the frame size. Frames that include464the uncompressed data size require less memory to decompress, especially465at higher compression levels.</p>466<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>, a467<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 of468a frame. If the pledged size does not match the actual size of data469provided 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> or470<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 may471be lost.</p>472<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 mode473<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 into474the header unless <code class="xref py py-meth docutils literal notranslate"><span class="pre">set_pledged_input_size()</span></code> is called again.</p>475</dd></dl>476 477<dl class="py attribute">478<dt class="sig sig-object py" id="compression.zstd.ZstdCompressor.CONTINUE">479<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>480<dd><p>Collect more data for compression, which may or may not generate output481immediately. This mode optimizes the compression ratio by maximizing the482amount of data per block and frame.</p>483</dd></dl>484 485<dl class="py attribute">486<dt class="sig sig-object py" id="compression.zstd.ZstdCompressor.FLUSH_BLOCK">487<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>488<dd><p>Complete and write a block to the data stream. The data returned so far489can be immediately decompressed. Past data can still be referenced in490future 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>,491improving compression.</p>492</dd></dl>493 494<dl class="py attribute">495<dt class="sig sig-object py" id="compression.zstd.ZstdCompressor.FLUSH_FRAME">496<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>497<dd><p>Complete and write out a frame. Future data provided to498<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 and499<em>cannot</em> reference past data.</p>500</dd></dl>501 502<dl class="py attribute">503<dt class="sig sig-object py" id="compression.zstd.ZstdCompressor.last_mode">504<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>505<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>.506The 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>, or507<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>,508signifying that the compressor is at the start of a new frame.</p>509</dd></dl>510 511</dd></dl>512 513<dl class="py class">514<dt class="sig sig-object py" id="compression.zstd.ZstdDecompressor">515<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>516<dd><p>Create a decompressor object, which can be used to decompress data517incrementally.</p>518<p>For a more convenient way of decompressing an entire compressed stream at519once, 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>520<p>The <em>options</em> argument is a Python dictionary containing advanced521decompression parameters. The valid keys and values for compression522parameters 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>523documentation.</p>524<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>525containing trained data used during compression. This must be526the same Zstandard dictionary used during compression.</p>527<div class="admonition note">528<p class="admonition-title">Note</p>529<p>This class does not transparently handle inputs containing multiple530compressed 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 and531<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 should532use <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 a533<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>534</div>535<dl class="py method">536<dt class="sig sig-object py" id="compression.zstd.ZstdDecompressor.decompress">537<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>538<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>), returning539uncompressed data as bytes. Some of <em>data</em> may be buffered540internally, for use in later calls to <code class="xref py py-meth docutils literal notranslate"><span class="pre">decompress()</span></code>.541The returned data should be concatenated with the output of any previous542calls to <code class="xref py py-meth docutils literal notranslate"><span class="pre">decompress()</span></code>.</p>543<p>If <em>max_length</em> is non-negative, the method returns at most <em>max_length</em>544bytes of decompressed data. If this limit is reached and further545output 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 will546be set to <code class="docutils literal notranslate"><span class="pre">False</span></code>. In this case, the next call to547<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 obtain548more of the output.</p>549<p>If all of the input data was decompressed and returned (either550because this was less than <em>max_length</em> bytes, or because551<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> attribute552will be set to <code class="docutils literal notranslate"><span class="pre">True</span></code>.</p>553<p>Attempting to decompress data after the end of a frame will raise a554<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 ignored555and 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>556</dd></dl>557 558<dl class="py attribute">559<dt class="sig sig-object py" id="compression.zstd.ZstdDecompressor.eof">560<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>561<dd><p><code class="docutils literal notranslate"><span class="pre">True</span></code> if the end-of-stream marker has been reached.</p>562</dd></dl>563 564<dl class="py attribute">565<dt class="sig sig-object py" id="compression.zstd.ZstdDecompressor.unused_data">566<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>567<dd><p>Data found after the end of the compressed stream.</p>568<p>Before the end of the stream is reached, this will be <code class="docutils literal notranslate"><span class="pre">b''</span></code>.</p>569</dd></dl>570 571<dl class="py attribute">572<dt class="sig sig-object py" id="compression.zstd.ZstdDecompressor.needs_input">573<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>574<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 more575decompressed data before requiring new compressed input.</p>576</dd></dl>577 578</dd></dl>579 580</section>581<section id="zstandard-dictionaries">582<h2>Zstandard dictionaries<a class="headerlink" href="#zstandard-dictionaries" title="Link to this heading">¶</a></h2>583<dl class="py function">584<dt class="sig sig-object py" id="compression.zstd.train_dict">585<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>586<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.587Zstandard dictionaries enable more efficient compression of smaller sizes588of data, which is traditionally difficult to compress due to less589repetition. If you are compressing multiple similar groups of data (such as590similar files), Zstandard dictionaries can improve compression ratios and591speed significantly.</p>592<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 the593population of samples used to train the Zstandard dictionary.</p>594<p>The <em>dict_size</em> argument, an integer, is the maximum size (in bytes) the595Zstandard dictionary should be. The Zstandard documentation suggests an596absolute maximum of no more than 100 KB, but the maximum can often be smaller597depending on the data. Larger dictionaries generally slow down compression,598but improve compression ratios. Smaller dictionaries lead to faster599compression, but reduce the compression ratio.</p>600</dd></dl>601 602<dl class="py function">603<dt class="sig sig-object py" id="compression.zstd.finalize_dict">604<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>605<dd><p>An advanced function for converting a “raw content” Zstandard dictionary into606a regular Zstandard dictionary. “Raw content” dictionaries are a sequence of607bytes that do not need to follow the structure of a normal Zstandard608dictionary.</p>609<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 with610the <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>611<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), contains612sample data for generating the Zstandard dictionary.</p>613<p>The <em>dict_size</em> argument, an integer, is the maximum size (in bytes) the614Zstandard 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> for615suggestions on the maximum dictionary size.</p>616<p>The <em>level</em> argument (an integer) is the compression level expected to be617passed to the compressors using this dictionary. The dictionary information618varies for each compression level, so tuning for the proper compression619level can make compression more efficient.</p>620</dd></dl>621 622<dl class="py class">623<dt class="sig sig-object py" id="compression.zstd.ZstdDict">624<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>625<dd><p>A wrapper around Zstandard dictionaries. Dictionaries can be used to improve626the 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 you627need to train a new dictionary from sample data.</p>628<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 already629trained dictionary information.</p>630<p>The <em>is_raw</em> argument, a boolean, is an advanced parameter controlling the631meaning 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”632dictionary, without any format restrictions. <code class="docutils literal notranslate"><span class="pre">False</span></code> means <em>dict_content</em>633is an ordinary Zstandard dictionary, created from Zstandard functions,634for 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>635<p>When passing a <code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdDict</span></code> to a function, the636<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 can637control how the dictionary is loaded by passing them as the <code class="docutils literal notranslate"><span class="pre">zstd_dict</span></code>638argument, for example, <code class="docutils literal notranslate"><span class="pre">compress(data,</span> <span class="pre">zstd_dict=zd.as_digested_dict)</span></code>.639Digesting a dictionary is a costly operation that occurs when loading a640Zstandard dictionary. When making multiple calls to compression or641decompression, passing a digested dictionary will reduce the overhead of642loading the dictionary.</p>643<blockquote>644<div><table class="docutils align-default" id="id1">645<caption><span class="caption-text">Difference for compression</span><a class="headerlink" href="#id1" title="Link to this table">¶</a></caption>646<colgroup>647<col style="width: 29.4%" />648<col style="width: 41.2%" />649<col style="width: 29.4%" />650</colgroup>651<thead>652<tr class="row-odd"><th class="head"></th>653<th class="head"><p>Digested dictionary</p></th>654<th class="head"><p>Undigested dictionary</p></th>655</tr>656</thead>657<tbody>658<tr class="row-even"><td><p>Advanced parameters of the compressor which may be overridden by659the dictionary’s parameters</p></td>660<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>,661<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>,662<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>,663<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>,664and some non-public parameters.</p></td>665<td><p>None</p></td>666</tr>667<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>668<td><p>Yes. It’s faster when loading a digested dictionary again with the669same compression level.</p></td>670<td><p>No. If you wish to load an undigested dictionary multiple times,671consider reusing a compressor object.</p></td>672</tr>673</tbody>674</table>675</div></blockquote>676<p>If passing a <code class="xref py py-class docutils literal notranslate"><span class="pre">ZstdDict</span></code> without any attribute, an undigested677dictionary is passed by default when compressing and a digested dictionary678is generated if necessary and passed by default when decompressing.</p>679<blockquote>680<div><dl class="py attribute">681<dt class="sig sig-object py" id="compression.zstd.ZstdDict.dict_content">682<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>683<dd><p>The content of the Zstandard dictionary, a <code class="docutils literal notranslate"><span class="pre">bytes</span></code> object. It’s the684same as the <em>dict_content</em> argument in the <code class="docutils literal notranslate"><span class="pre">__init__</span></code> method. It can685be used with other programs, such as the <code class="docutils literal notranslate"><span class="pre">zstd</span></code> CLI program.</p>686</dd></dl>687 688<dl class="py attribute">689<dt class="sig sig-object py" id="compression.zstd.ZstdDict.dict_id">690<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>691<dd><p>Identifier of the Zstandard dictionary, a non-negative int value.</p>692<p>Non-zero means the dictionary is ordinary, created by Zstandard693functions and following the Zstandard format.</p>694<p><code class="docutils literal notranslate"><span class="pre">0</span></code> means a “raw content” dictionary, free of any format restriction,695used for advanced users.</p>696<div class="admonition note">697<p class="admonition-title">Note</p>698<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 different699from 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>700function.</p>701</div>702</dd></dl>703 704<dl class="py attribute">705<dt class="sig sig-object py" id="compression.zstd.ZstdDict.as_digested_dict">706<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>707<dd><p>Load as a digested dictionary.</p>708</dd></dl>709 710<dl class="py attribute">711<dt class="sig sig-object py" id="compression.zstd.ZstdDict.as_undigested_dict">712<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>713<dd><p>Load as an undigested dictionary.</p>714</dd></dl>715 716</div></blockquote>717</dd></dl>718 719</section>720<section id="advanced-parameter-control">721<h2>Advanced parameter control<a class="headerlink" href="#advanced-parameter-control" title="Link to this heading">¶</a></h2>722<dl class="py class">723<dt class="sig sig-object py" id="compression.zstd.CompressionParameter">724<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>725<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 parameter726keys that can be used when compressing data.</p>727<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 valid728values for that parameter.</p>729<p>Parameters are optional; any omitted parameter will have it’s value selected730automatically.</p>731<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>732<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>733</pre></div>734</div>735<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>736<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>737<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>738<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>739</pre></div>740</div>741<dl class="py method">742<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.bounds">743<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>744<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 compression745parameter. This method should be called on the attribute you wish to746retrieve the bounds of. For example, to get the valid values for747<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 of748<code class="docutils literal notranslate"><span class="pre">CompressionParameter.compression_level.bounds()</span></code>.</p>749<p>Both the lower and upper bounds are inclusive.</p>750</dd></dl>751 752<dl class="py attribute">753<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.compression_level">754<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>755<dd><p>A high-level means of setting other compression parameters that affect756the speed and ratio of compressing data.</p>757<p>Regular compression levels are greater than <code class="docutils literal notranslate"><span class="pre">0</span></code>. Values greater than758<code class="docutils literal notranslate"><span class="pre">20</span></code> are considered “ultra” compression and require more memory than759other levels. Negative values can be used to trade off faster compression760for worse compression ratios.</p>761<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>762</dd></dl>763 764<dl class="py attribute">765<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.window_log">766<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>767<dd><p>Maximum allowed back-reference distance the compressor can use when768compressing 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.769This parameter greatly influences the memory usage of compression. Higher770values require more memory but gain better compression values.</p>771<p>A value of zero causes the value to be selected automatically.</p>772</dd></dl>773 774<dl class="py attribute">775<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.hash_log">776<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>777<dd><p>Size of the initial probe table, as a power of two. The resulting memory778usage 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 compression779ratio 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 compression780speed of strategies &gt; <code class="xref py py-attr docutils literal notranslate"><span class="pre">dfast</span></code>.</p>781<p>A value of zero causes the value to be selected automatically.</p>782</dd></dl>783 784<dl class="py attribute">785<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.chain_log">786<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>787<dd><p>Size of the multi-probe search table, as a power of two. The resulting788memory 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 in789better and slower compression. This parameter has no effect for the790<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 using791<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 secondary792probe table.</p>793<p>A value of zero causes the value to be selected automatically.</p>794</dd></dl>795 796<dl class="py attribute">797<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.search_log">798<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>799<dd><p>Number of search attempts, as a power of two. More attempts result in800better and slower compression. This parameter is useless for801<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>802<p>A value of zero causes the value to be selected automatically.</p>803</dd></dl>804 805<dl class="py attribute">806<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.min_match">807<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>808<dd><p>Minimum size of searched matches. Larger values increase compression and809decompression speed, but decrease ratio. Note that Zstandard can still810find matches of smaller size, it just tweaks its search algorithm to look811for 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>,812the effective minimum is <code class="docutils literal notranslate"><span class="pre">4</span></code>; for all strategies813&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>814<p>A value of zero causes the value to be selected automatically.</p>815</dd></dl>816 817<dl class="py attribute">818<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.target_length">819<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>820<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>821<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> and822<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 match823considered “good enough” to stop searching. Larger values make824compression ratios better, but compresses slower.</p>825<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 match826sampling. Larger values make compression faster, but with a worse827compression ratio.</p>828<p>A value of zero causes the value to be selected automatically.</p>829</dd></dl>830 831<dl class="py attribute">832<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.strategy">833<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>834<dd><p>The higher the value of selected strategy, the more complex the835compression technique used by zstd, resulting in higher compression836ratios but slower compression.</p>837<div class="admonition seealso">838<p class="admonition-title">See also</p>839<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>840</div>841</dd></dl>842 843<dl class="py attribute">844<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.enable_long_distance_matching">845<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>846<dd><p>Long distance matching can be used to improve compression for large847inputs by finding large matches at greater distances. It increases memory848usage and window size.</p>849<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>850disable it.</p>851<p>Enabling this parameter increases default852<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 expressly853set to a different value. This setting is enabled by default if854<code class="xref py py-attr docutils literal notranslate"><span class="pre">window_log</span></code> &gt;= 128 MiB and the compression855strategy &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>856</dd></dl>857 858<dl class="py attribute">859<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.ldm_hash_log">860<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>861<dd><p>Size of the table for long distance matching, as a power of two. Larger862values increase memory usage and compression ratio, but decrease863compression speed.</p>864<p>A value of zero causes the value to be selected automatically.</p>865</dd></dl>866 867<dl class="py attribute">868<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.ldm_min_match">869<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>870<dd><p>Minimum match size for long distance matcher. Larger or too small values871can often decrease the compression ratio.</p>872<p>A value of zero causes the value to be selected automatically.</p>873</dd></dl>874 875<dl class="py attribute">876<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.ldm_bucket_size_log">877<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>878<dd><p>Log size of each bucket in the long distance matcher hash table for879collision resolution. Larger values improve collision resolution but880decrease compression speed.</p>881<p>A value of zero causes the value to be selected automatically.</p>882</dd></dl>883 884<dl class="py attribute">885<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.ldm_hash_rate_log">886<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>887<dd><p>Frequency of inserting/looking up entries into the long distance matcher888hash table. Larger values improve compression speed. Deviating far from889the default value will likely result in a compression ratio decrease.</p>890<p>A value of zero causes the value to be selected automatically.</p>891</dd></dl>892 893<dl class="py attribute">894<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.content_size_flag">895<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>896<dd><p>Write the size of the data to be compressed into the Zstandard frame897header when known prior to compressing.</p>898<p>This flag only takes effect under the following scenarios:</p>899<ul class="simple">900<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>901<li><p>Providing all of the data to be compressed in the frame in a single902<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 the903<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>904<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 exact905amount of data that will be provided to the compressor prior to any906calls 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.907<code class="xref py py-meth docutils literal notranslate"><span class="pre">ZstdCompressor.set_pledged_input_size()</span></code> must be called for each908new frame.</p></li>909</ul>910<p>All other compression calls may not write the size information into the911frame header.</p>912<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>913disable it.</p>914</dd></dl>915 916<dl class="py attribute">917<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.checksum_flag">918<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>919<dd><p>A four-byte checksum using XXHash64 of the uncompressed content is920written at the end of each frame. Zstandard’s decompression code verifies921the 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 is922raised.</p>923<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>924disable it.</p>925</dd></dl>926 927<dl class="py attribute">928<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.dict_id_flag">929<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>930<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 written931into the frame header.</p>932<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> or933<code class="docutils literal notranslate"><span class="pre">0</span></code> disable it.</p>934</dd></dl>935 936<dl class="py attribute">937<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.nb_workers">938<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>939<dd><p>Select how many threads will be spawned to compress in parallel. When940<code class="xref py py-attr docutils literal notranslate"><span class="pre">nb_workers</span></code> &gt; 0, enables multi-threaded compression, a value of941<code class="docutils literal notranslate"><span class="pre">1</span></code> means “one-thread multi-threaded mode”. More workers improve speed,942but also increase memory usage and slightly reduce compression ratio.</p>943<p>A value of zero disables multi-threading.</p>944</dd></dl>945 946<dl class="py attribute">947<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.job_size">948<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>949<dd><p>Size of a compression job, in bytes. This value is enforced only when950<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 is951completed in parallel, so this value can indirectly impact the number of952active threads.</p>953<p>A value of zero causes the value to be selected automatically.</p>954</dd></dl>955 956<dl class="py attribute">957<dt class="sig sig-object py" id="compression.zstd.CompressionParameter.overlap_log">958<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>959<dd><p>Sets how much data is reloaded from previous jobs (threads) for new jobs960to be used by the look behind window during compression. This value is961only 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. Acceptable962values vary from 0 to 9.</p>963<blockquote>964<div><ul class="simple">965<li><p>0 means dynamically set the overlap amount</p></li>966<li><p>1 means no overlap</p></li>967<li><p>9 means use a full window size from the previous job</p></li>968</ul>969</div></blockquote>970<p>Each increment halves/doubles the overlap size. “8” means an overlap of971<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>972</dd></dl>973 974</dd></dl>975 976<dl class="py class">977<dt class="sig sig-object py" id="compression.zstd.DecompressionParameter">978<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>979<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 parameter980keys that can be used when decompressing data. Parameters are optional; any981omitted parameter will have it’s value selected automatically.</p>982<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 valid983values for that parameter.</p>984<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>985<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>986 987<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>988 989<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>990<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>991</pre></div>992</div>993<dl class="py method">994<dt class="sig sig-object py" id="compression.zstd.DecompressionParameter.bounds">995<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>996<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 decompression997parameter. This method should be called on the attribute you wish to998retrieve the bounds of.</p>999<p>Both the lower and upper bounds are inclusive.</p>1000</dd></dl>1001 1002<dl class="py attribute">1003<dt class="sig sig-object py" id="compression.zstd.DecompressionParameter.window_log_max">1004<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>1005<dd><p>The base-two logarithm of the maximum size of the window used during1006decompression. This can be useful to limit the amount of memory used when1007decompressing data. A larger maximum window size leads to faster1008decompression.</p>1009<p>A value of zero causes the value to be selected automatically.</p>1010</dd></dl>1011 1012</dd></dl>1013 1014<dl class="py class">1015<dt class="sig sig-object py" id="compression.zstd.Strategy">1016<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>1017<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.1018Higher-numbered strategies correspond to more complex and slower1019compression.</p>1020<div class="admonition note">1021<p class="admonition-title">Note</p>1022<p>The values of attributes of <code class="xref py py-class docutils literal notranslate"><span class="pre">Strategy</span></code> are not necessarily stable1023across zstd versions. Only the ordering of the attributes may be relied1024upon. The attributes are listed below in order.</p>1025</div>1026<p>The following strategies are available:</p>1027<dl class="py attribute">1028<dt class="sig sig-object py" id="compression.zstd.Strategy.fast">1029<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>1030<dd></dd></dl>1031 1032<dl class="py attribute">1033<dt class="sig sig-object py" id="compression.zstd.Strategy.dfast">1034<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>1035<dd></dd></dl>1036 1037<dl class="py attribute">1038<dt class="sig sig-object py" id="compression.zstd.Strategy.greedy">1039<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>1040<dd></dd></dl>1041 1042<dl class="py attribute">1043<dt class="sig sig-object py" id="compression.zstd.Strategy.lazy">1044<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>1045<dd></dd></dl>1046 1047<dl class="py attribute">1048<dt class="sig sig-object py" id="compression.zstd.Strategy.lazy2">1049<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>1050<dd></dd></dl>1051 1052<dl class="py attribute">1053<dt class="sig sig-object py" id="compression.zstd.Strategy.btlazy2">1054<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>1055<dd></dd></dl>1056 1057<dl class="py attribute">1058<dt class="sig sig-object py" id="compression.zstd.Strategy.btopt">1059<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>1060<dd></dd></dl>1061 1062<dl class="py attribute">1063<dt class="sig sig-object py" id="compression.zstd.Strategy.btultra">1064<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>1065<dd></dd></dl>1066 1067<dl class="py attribute">1068<dt class="sig sig-object py" id="compression.zstd.Strategy.btultra2">1069<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>1070<dd></dd></dl>1071 1072</dd></dl>1073 1074</section>1075<section id="miscellaneous">1076<h2>Miscellaneous<a class="headerlink" href="#miscellaneous" title="Link to this heading">¶</a></h2>1077<dl class="py function">1078<dt class="sig sig-object py" id="compression.zstd.get_frame_info">1079<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>1080<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 Zstandard1081frame. Frames contain metadata related to the compressed data they hold.</p>1082</dd></dl>1083 1084<dl class="py class">1085<dt class="sig sig-object py" id="compression.zstd.FrameInfo">1086<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>1087<dd><p>Metadata related to a Zstandard frame.</p>1088<dl class="py attribute">1089<dt class="sig sig-object py" id="compression.zstd.FrameInfo.decompressed_size">1090<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>1091<dd><p>The size of the decompressed contents of the frame.</p>1092</dd></dl>1093 1094<dl class="py attribute">1095<dt class="sig sig-object py" id="compression.zstd.FrameInfo.dictionary_id">1096<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>1097<dd><p>An integer representing the Zstandard dictionary ID needed for1098decompressing the frame. <code class="docutils literal notranslate"><span class="pre">0</span></code> means the dictionary ID was not1099recorded in the frame header. This may mean that a Zstandard dictionary1100is not needed, or that the ID of a required dictionary was not recorded.</p>1101</dd></dl>1102 1103</dd></dl>1104 1105<dl class="py attribute">1106<dt class="sig sig-object py" id="compression.zstd.COMPRESSION_LEVEL_DEFAULT">1107<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>1108<dd><p>The default compression level for Zstandard: <code class="docutils literal notranslate"><span class="pre">3</span></code>.</p>1109</dd></dl>1110 1111<dl class="py attribute">1112<dt class="sig sig-object py" id="compression.zstd.zstd_version_info">1113<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>1114<dd><p>Version number of the runtime zstd library as a tuple of integers1115(major, minor, release).</p>1116</dd></dl>1117 1118</section>1119<section id="examples">1120<h2>Examples<a class="headerlink" href="#examples" title="Link to this heading">¶</a></h2>1121<p>Reading in a compressed file:</p>1122<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>1123 1124<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>1125    <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>1126</pre></div>1127</div>1128<p>Creating a compressed file:</p>1129<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>1130 1131<span class="n">data</span> <span class="o">=</span> <span class="sa">b</span><span class="s2">&quot;Insert Data Here&quot;</span>1132<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>1133    <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>1134</pre></div>1135</div>1136<p>Compressing data in memory:</p>1137<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>1138 1139<span class="n">data_in</span> <span class="o">=</span> <span class="sa">b</span><span class="s2">&quot;Insert Data Here&quot;</span>1140<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>1141</pre></div>1142</div>1143<p>Incremental compression:</p>1144<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>1145 1146<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>1147<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>1148<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>1149<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>1150<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>1151<span class="c1"># Concatenate all the partial results:</span>1152<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>1153</pre></div>1154</div>1155<p>Writing compressed data to an already-open file:</p>1156<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>1157 1158<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>1159    <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>1160    <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>1161        <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>1162    <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>1163</pre></div>1164</div>1165<p>Creating a compressed file using compression parameters:</p>1166<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>1167 1168<span class="n">options</span> <span class="o">=</span> <span class="p">{</span>1169   <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>1170<span class="p">}</span>1171<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>1172    <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>1173</pre></div>1174</div>1175</section>1176</section>1177 1178 1179            <div class="clearer"></div>1180          </div>1181        </div>1182      </div>1183      <div class="sphinxsidebar" role="navigation" aria-label="Main">1184        <div class="sphinxsidebarwrapper">1185  <div>1186    <h3><a href="../contents.html">Table of Contents</a></h3>1187    <ul>1188<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>1189<li><a class="reference internal" href="#exceptions">Exceptions</a></li>1190<li><a class="reference internal" href="#reading-and-writing-compressed-files">Reading and writing compressed files</a></li>1191<li><a class="reference internal" href="#compressing-and-decompressing-data-in-memory">Compressing and decompressing data in memory</a></li>1192<li><a class="reference internal" href="#zstandard-dictionaries">Zstandard dictionaries</a></li>1193<li><a class="reference internal" href="#advanced-parameter-control">Advanced parameter control</a></li>1194<li><a class="reference internal" href="#miscellaneous">Miscellaneous</a></li>1195<li><a class="reference internal" href="#examples">Examples</a></li>1196</ul>1197</li>1198</ul>1199 1200  </div>

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