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  98. <li><a class="reference internal" href="#"><code class="xref py py-mod docutils literal notranslate"><span class="pre">bz2</span></code> — Support for <strong class="program">bzip2</strong> compression</a><ul>

  99. <li><a class="reference internal" href="#de-compression-of-files">(De)compression of files</a></li>

  100. <li><a class="reference internal" href="#incremental-de-compression">Incremental (de)compression</a></li>

  101. <li><a class="reference internal" href="#one-shot-de-compression">One-shot (de)compression</a></li>

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  195.   <section id="module-bz2">

  196. <span id="bz2-support-for-bzip2-compression"></span><h1><a class="reference internal" href="#module-bz2" title="bz2: Interfaces for bzip2 compression and decompression."><code class="xref py py-mod docutils literal notranslate"><span class="pre">bz2</span></code></a> — Support for <strong class="program">bzip2</strong> compression<a class="headerlink" href="#module-bz2" title="Link to this heading">¶</a></h1>

  197. <p><strong>Source code:</strong> <a class="reference external" href="https://github.com/python/cpython/tree/3.12/Lib/bz2.py">Lib/bz2.py</a></p>

  198. <hr class="docutils" />

  199. <p>This module provides a comprehensive interface for compressing and

  200. decompressing data using the bzip2 compression algorithm.</p>

  201. <p>The <a class="reference internal" href="#module-bz2" title="bz2: Interfaces for bzip2 compression and decompression."><code class="xref py py-mod docutils literal notranslate"><span class="pre">bz2</span></code></a> module contains:</p>

  202. <ul class="simple">

  203. <li><p>The <a class="reference internal" href="#bz2.open" title="bz2.open"><code class="xref py py-func docutils literal notranslate"><span class="pre">open()</span></code></a> function and <a class="reference internal" href="#bz2.BZ2File" title="bz2.BZ2File"><code class="xref py py-class docutils literal notranslate"><span class="pre">BZ2File</span></code></a> class for reading and

  204. writing compressed files.</p></li>

  205. <li><p>The <a class="reference internal" href="#bz2.BZ2Compressor" title="bz2.BZ2Compressor"><code class="xref py py-class docutils literal notranslate"><span class="pre">BZ2Compressor</span></code></a> and <a class="reference internal" href="#bz2.BZ2Decompressor" title="bz2.BZ2Decompressor"><code class="xref py py-class docutils literal notranslate"><span class="pre">BZ2Decompressor</span></code></a> classes for

  206. incremental (de)compression.</p></li>

  207. <li><p>The <a class="reference internal" href="#bz2.compress" title="bz2.compress"><code class="xref py py-func docutils literal notranslate"><span class="pre">compress()</span></code></a> and <a class="reference internal" href="#bz2.decompress" title="bz2.decompress"><code class="xref py py-func docutils literal notranslate"><span class="pre">decompress()</span></code></a> functions for one-shot

  208. (de)compression.</p></li>

  209. </ul>

  210. <section id="de-compression-of-files">

  211. <h2>(De)compression of files<a class="headerlink" href="#de-compression-of-files" title="Link to this heading">¶</a></h2>

  212. <dl class="py function">

  213. <dt class="sig sig-object py" id="bz2.open">

  214. <span class="sig-prename descclassname"><span class="pre">bz2.</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">filename</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">'rb'</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">compresslevel</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">9</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="#bz2.open" title="Link to this definition">¶</a></dt>

  215. <dd><p>Open a bzip2-compressed file in binary or text mode, returning a <a class="reference internal" href="../glossary.html#term-file-object"><span class="xref std std-term">file

  216. object</span></a>.</p>

  217. <p>As with the constructor for <a class="reference internal" href="#bz2.BZ2File" title="bz2.BZ2File"><code class="xref py py-class docutils literal notranslate"><span class="pre">BZ2File</span></code></a>, the <em>filename</em> argument can be

  218. an actual filename (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> or <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), or an existing

  219. file object to read from or write to.</p>

  220. <p>The <em>mode</em> argument can be any of <code class="docutils literal notranslate"><span class="pre">'r'</span></code>, <code class="docutils literal notranslate"><span class="pre">'rb'</span></code>, <code class="docutils literal notranslate"><span class="pre">'w'</span></code>, <code class="docutils literal notranslate"><span class="pre">'wb'</span></code>,

  221. <code class="docutils literal notranslate"><span class="pre">'x'</span></code>, <code class="docutils literal notranslate"><span class="pre">'xb'</span></code>, <code class="docutils literal notranslate"><span class="pre">'a'</span></code> or <code class="docutils literal notranslate"><span class="pre">'ab'</span></code> for binary mode, or <code class="docutils literal notranslate"><span class="pre">'rt'</span></code>,

  222. <code class="docutils literal notranslate"><span class="pre">'wt'</span></code>, <code class="docutils literal notranslate"><span class="pre">'xt'</span></code>, or <code class="docutils literal notranslate"><span class="pre">'at'</span></code> for text mode. The default is <code class="docutils literal notranslate"><span class="pre">'rb'</span></code>.</p>

  223. <p>The <em>compresslevel</em> argument is an integer from 1 to 9, as for the

  224. <a class="reference internal" href="#bz2.BZ2File" title="bz2.BZ2File"><code class="xref py py-class docutils literal notranslate"><span class="pre">BZ2File</span></code></a> constructor.</p>

  225. <p>For binary mode, this function is equivalent to the <a class="reference internal" href="#bz2.BZ2File" title="bz2.BZ2File"><code class="xref py py-class docutils literal notranslate"><span class="pre">BZ2File</span></code></a>

  226. constructor: <code class="docutils literal notranslate"><span class="pre">BZ2File(filename,</span> <span class="pre">mode,</span> <span class="pre">compresslevel=compresslevel)</span></code>. In

  227. this case, the <em>encoding</em>, <em>errors</em> and <em>newline</em> arguments must not be

  228. provided.</p>

  229. <p>For text mode, a <a class="reference internal" href="#bz2.BZ2File" title="bz2.BZ2File"><code class="xref py py-class docutils literal notranslate"><span class="pre">BZ2File</span></code></a> object is created, and wrapped in an

  230. <a class="reference internal" href="io.html#io.TextIOWrapper" title="io.TextIOWrapper"><code class="xref py py-class docutils literal notranslate"><span class="pre">io.TextIOWrapper</span></code></a> instance with the specified encoding, error

  231. handling behavior, and line ending(s).</p>

  232. <div class="versionadded">

  233. <p><span class="versionmodified added">New in version 3.3.</span></p>

  234. </div>

  235. <div class="versionchanged">

  236. <p><span class="versionmodified changed">Changed in version 3.4: </span>The <code class="docutils literal notranslate"><span class="pre">'x'</span></code> (exclusive creation) mode was added.</p>

  237. </div>

  238. <div class="versionchanged">

  239. <p><span class="versionmodified changed">Changed in version 3.6: </span>Accepts a <a class="reference internal" href="../glossary.html#term-path-like-object"><span class="xref std std-term">path-like object</span></a>.</p>

  240. </div>

  241. </dd></dl>

  242. 

  243. <dl class="py class">

  244. <dt class="sig sig-object py" id="bz2.BZ2File">

  245. <em class="property"><span class="pre">class</span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">bz2.</span></span><span class="sig-name descname"><span class="pre">BZ2File</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">filename</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">'r'</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">*</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">compresslevel</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">9</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#bz2.BZ2File" title="Link to this definition">¶</a></dt>

  246. <dd><p>Open a bzip2-compressed file in binary mode.</p>

  247. <p>If <em>filename</em> is 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> or <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, open the named file

  248. directly. Otherwise, <em>filename</em> should be a <a class="reference internal" href="../glossary.html#term-file-object"><span class="xref std std-term">file object</span></a>, which will

  249. be used to read or write the compressed data.</p>

  250. <p>The <em>mode</em> argument can be either <code class="docutils literal notranslate"><span class="pre">'r'</span></code> for reading (default), <code class="docutils literal notranslate"><span class="pre">'w'</span></code> for

  251. overwriting, <code class="docutils literal notranslate"><span class="pre">'x'</span></code> for exclusive creation, or <code class="docutils literal notranslate"><span class="pre">'a'</span></code> for appending. These

  252. can equivalently be given as <code class="docutils literal notranslate"><span class="pre">'rb'</span></code>, <code class="docutils literal notranslate"><span class="pre">'wb'</span></code>, <code class="docutils literal notranslate"><span class="pre">'xb'</span></code> and <code class="docutils literal notranslate"><span class="pre">'ab'</span></code>

  253. respectively.</p>

  254. <p>If <em>filename</em> is a file object (rather than an actual file name), a mode of

  255. <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>

  256. <p>If <em>mode</em> is <code class="docutils literal notranslate"><span class="pre">'w'</span></code> or <code class="docutils literal notranslate"><span class="pre">'a'</span></code>, <em>compresslevel</em> can be an integer between

  257. <code class="docutils literal notranslate"><span class="pre">1</span></code> and <code class="docutils literal notranslate"><span class="pre">9</span></code> specifying the level of compression: <code class="docutils literal notranslate"><span class="pre">1</span></code> produces the

  258. least compression, and <code class="docutils literal notranslate"><span class="pre">9</span></code> (default) produces the most compression.</p>

  259. <p>If <em>mode</em> is <code class="docutils literal notranslate"><span class="pre">'r'</span></code>, the input file may be the concatenation of multiple

  260. compressed streams.</p>

  261. <p><a class="reference internal" href="#bz2.BZ2File" title="bz2.BZ2File"><code class="xref py py-class docutils literal notranslate"><span class="pre">BZ2File</span></code></a> provides all of the members specified by the

  262. <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>

  263. and <a class="reference internal" href="io.html#io.IOBase.truncate" title="io.IOBase.truncate"><code class="xref py py-meth docutils literal notranslate"><span class="pre">truncate()</span></code></a>.

  264. Iteration and the <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">with</span></code></a> statement are supported.</p>

  265. <p><a class="reference internal" href="#bz2.BZ2File" title="bz2.BZ2File"><code class="xref py py-class docutils literal notranslate"><span class="pre">BZ2File</span></code></a> also provides the following methods:</p>

  266. <dl class="py method">

  267. <dt class="sig sig-object py" id="bz2.BZ2File.peek">

  268. <span class="sig-name descname"><span class="pre">peek</span></span><span class="sig-paren">(</span><span class="optional">[</span><em class="sig-param"><span class="n"><span class="pre">n</span></span></em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bz2.BZ2File.peek" title="Link to this definition">¶</a></dt>

  269. <dd><p>Return buffered data without advancing the file position. At least one

  270. byte of data will be returned (unless at EOF). The exact number of bytes

  271. returned is unspecified.</p>

  272. <div class="admonition note">

  273. <p class="admonition-title">Note</p>

  274. <p>While calling <a class="reference internal" href="#bz2.BZ2File.peek" title="bz2.BZ2File.peek"><code class="xref py py-meth docutils literal notranslate"><span class="pre">peek()</span></code></a> does not change the file position of

  275. the <a class="reference internal" href="#bz2.BZ2File" title="bz2.BZ2File"><code class="xref py py-class docutils literal notranslate"><span class="pre">BZ2File</span></code></a>, it may change the position of the underlying file

  276. object (e.g. if the <a class="reference internal" href="#bz2.BZ2File" title="bz2.BZ2File"><code class="xref py py-class docutils literal notranslate"><span class="pre">BZ2File</span></code></a> was constructed by passing a file

  277. object for <em>filename</em>).</p>

  278. </div>

  279. <div class="versionadded">

  280. <p><span class="versionmodified added">New in version 3.3.</span></p>

  281. </div>

  282. </dd></dl>

  283. 

  284. <dl class="py method">

  285. <dt class="sig sig-object py" id="bz2.BZ2File.fileno">

  286. <span class="sig-name descname"><span class="pre">fileno</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bz2.BZ2File.fileno" title="Link to this definition">¶</a></dt>

  287. <dd><p>Return the file descriptor for the underlying file.</p>

  288. <div class="versionadded">

  289. <p><span class="versionmodified added">New in version 3.3.</span></p>

  290. </div>

  291. </dd></dl>

  292. 

  293. <dl class="py method">

  294. <dt class="sig sig-object py" id="bz2.BZ2File.readable">

  295. <span class="sig-name descname"><span class="pre">readable</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bz2.BZ2File.readable" title="Link to this definition">¶</a></dt>

  296. <dd><p>Return whether the file was opened for reading.</p>

  297. <div class="versionadded">

  298. <p><span class="versionmodified added">New in version 3.3.</span></p>

  299. </div>

  300. </dd></dl>

  301. 

  302. <dl class="py method">

  303. <dt class="sig sig-object py" id="bz2.BZ2File.seekable">

  304. <span class="sig-name descname"><span class="pre">seekable</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bz2.BZ2File.seekable" title="Link to this definition">¶</a></dt>

  305. <dd><p>Return whether the file supports seeking.</p>

  306. <div class="versionadded">

  307. <p><span class="versionmodified added">New in version 3.3.</span></p>

  308. </div>

  309. </dd></dl>

  310. 

  311. <dl class="py method">

  312. <dt class="sig sig-object py" id="bz2.BZ2File.writable">

  313. <span class="sig-name descname"><span class="pre">writable</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bz2.BZ2File.writable" title="Link to this definition">¶</a></dt>

  314. <dd><p>Return whether the file was opened for writing.</p>

  315. <div class="versionadded">

  316. <p><span class="versionmodified added">New in version 3.3.</span></p>

  317. </div>

  318. </dd></dl>

  319. 

  320. <dl class="py method">

  321. <dt class="sig sig-object py" id="bz2.BZ2File.read1">

  322. <span class="sig-name descname"><span class="pre">read1</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="#bz2.BZ2File.read1" title="Link to this definition">¶</a></dt>

  323. <dd><p>Read up to <em>size</em> uncompressed bytes, while trying to avoid

  324. making multiple reads from the underlying stream. Reads up to a

  325. buffer’s worth of data if size is negative.</p>

  326. <p>Returns <code class="docutils literal notranslate"><span class="pre">b''</span></code> if the file is at EOF.</p>

  327. <div class="versionadded">

  328. <p><span class="versionmodified added">New in version 3.3.</span></p>

  329. </div>

  330. </dd></dl>

  331. 

  332. <dl class="py method">

  333. <dt class="sig sig-object py" id="bz2.BZ2File.readinto">

  334. <span class="sig-name descname"><span class="pre">readinto</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">b</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#bz2.BZ2File.readinto" title="Link to this definition">¶</a></dt>

  335. <dd><p>Read bytes into <em>b</em>.</p>

  336. <p>Returns the number of bytes read (0 for EOF).</p>

  337. <div class="versionadded">

  338. <p><span class="versionmodified added">New in version 3.3.</span></p>

  339. </div>

  340. </dd></dl>

  341. 

  342. <div class="versionchanged">

  343. <p><span class="versionmodified changed">Changed in version 3.1: </span>Support for the <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">with</span></code></a> statement was added.</p>

  344. </div>

  345. <div class="versionchanged">

  346. <p><span class="versionmodified changed">Changed in version 3.3: </span>Support was added for <em>filename</em> being a <a class="reference internal" href="../glossary.html#term-file-object"><span class="xref std std-term">file object</span></a> instead of an

  347. actual filename.</p>

  348. <p>The <code class="docutils literal notranslate"><span class="pre">'a'</span></code> (append) mode was added, along with support for reading

  349. multi-stream files.</p>

  350. </div>

  351. <div class="versionchanged">

  352. <p><span class="versionmodified changed">Changed in version 3.4: </span>The <code class="docutils literal notranslate"><span class="pre">'x'</span></code> (exclusive creation) mode was added.</p>

  353. </div>

  354. <div class="versionchanged">

  355. <p><span class="versionmodified changed">Changed in version 3.5: </span>The <a class="reference internal" href="io.html#io.BufferedIOBase.read" title="io.BufferedIOBase.read"><code class="xref py py-meth docutils literal notranslate"><span class="pre">read()</span></code></a> method now accepts an argument of

  356. <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p>

  357. </div>

  358. <div class="versionchanged">

  359. <p><span class="versionmodified changed">Changed in version 3.6: </span>Accepts a <a class="reference internal" href="../glossary.html#term-path-like-object"><span class="xref std std-term">path-like object</span></a>.</p>

  360. </div>

  361. <div class="versionchanged">

  362. <p><span class="versionmodified changed">Changed in version 3.9: </span>The <em>buffering</em> parameter has been removed. It was ignored and deprecated

  363. since Python 3.0. Pass an open file object to control how the file is

  364. opened.</p>

  365. <p>The <em>compresslevel</em> parameter became keyword-only.</p>

  366. </div>

  367. <div class="versionchanged">

  368. <p><span class="versionmodified changed">Changed in version 3.10: </span>This class is thread unsafe in the face of multiple simultaneous

  369. readers or writers, just like its equivalent classes in <a class="reference internal" href="gzip.html#module-gzip" title="gzip: Interfaces for gzip compression and decompression using file objects."><code class="xref py py-mod docutils literal notranslate"><span class="pre">gzip</span></code></a> and

  370. <a class="reference internal" href="lzma.html#module-lzma" title="lzma: A Python wrapper for the liblzma compression library."><code class="xref py py-mod docutils literal notranslate"><span class="pre">lzma</span></code></a> have always been.</p>

  371. </div>

  372. </dd></dl>

  373. 

  374. </section>

  375. <section id="incremental-de-compression">

  376. <h2>Incremental (de)compression<a class="headerlink" href="#incremental-de-compression" title="Link to this heading">¶</a></h2>

  377. <dl class="py class">

  378. <dt class="sig sig-object py" id="bz2.BZ2Compressor">

  379. <em class="property"><span class="pre">class</span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">bz2.</span></span><span class="sig-name descname"><span class="pre">BZ2Compressor</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">compresslevel</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">9</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#bz2.BZ2Compressor" title="Link to this definition">¶</a></dt>

  380. <dd><p>Create a new compressor object. This object may be used to compress data

  381. incrementally. For one-shot compression, use the <a class="reference internal" href="#bz2.compress" title="bz2.compress"><code class="xref py py-func docutils literal notranslate"><span class="pre">compress()</span></code></a> function

  382. instead.</p>

  383. <p><em>compresslevel</em>, if given, must be an integer between <code class="docutils literal notranslate"><span class="pre">1</span></code> and <code class="docutils literal notranslate"><span class="pre">9</span></code>. The

  384. default is <code class="docutils literal notranslate"><span class="pre">9</span></code>.</p>

  385. <dl class="py method">

  386. <dt class="sig sig-object py" id="bz2.BZ2Compressor.compress">

  387. <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><span class="sig-paren">)</span><a class="headerlink" href="#bz2.BZ2Compressor.compress" title="Link to this definition">¶</a></dt>

  388. <dd><p>Provide data to the compressor object. Returns a chunk of compressed data

  389. if possible, or an empty byte string otherwise.</p>

  390. <p>When you have finished providing data to the compressor, call the

  391. <a class="reference internal" href="#bz2.BZ2Compressor.flush" title="bz2.BZ2Compressor.flush"><code class="xref py py-meth docutils literal notranslate"><span class="pre">flush()</span></code></a> method to finish the compression process.</p>

  392. </dd></dl>

  393. 

  394. <dl class="py method">

  395. <dt class="sig sig-object py" id="bz2.BZ2Compressor.flush">

  396. <span class="sig-name descname"><span class="pre">flush</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bz2.BZ2Compressor.flush" title="Link to this definition">¶</a></dt>

  397. <dd><p>Finish the compression process. Returns the compressed data left in

  398. internal buffers.</p>

  399. <p>The compressor object may not be used after this method has been called.</p>

  400. </dd></dl>

  401. 

  402. </dd></dl>

  403. 

  404. <dl class="py class">

  405. <dt class="sig sig-object py" id="bz2.BZ2Decompressor">

  406. <em class="property"><span class="pre">class</span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">bz2.</span></span><span class="sig-name descname"><span class="pre">BZ2Decompressor</span></span><a class="headerlink" href="#bz2.BZ2Decompressor" title="Link to this definition">¶</a></dt>

  407. <dd><p>Create a new decompressor object. This object may be used to decompress data

  408. incrementally. For one-shot compression, use the <a class="reference internal" href="#bz2.decompress" title="bz2.decompress"><code class="xref py py-func docutils literal notranslate"><span class="pre">decompress()</span></code></a> function

  409. instead.</p>

  410. <div class="admonition note">

  411. <p class="admonition-title">Note</p>

  412. <p>This class does not transparently handle inputs containing multiple

  413. compressed streams, unlike <a class="reference internal" href="#bz2.decompress" title="bz2.decompress"><code class="xref py py-func docutils literal notranslate"><span class="pre">decompress()</span></code></a> and <a class="reference internal" href="#bz2.BZ2File" title="bz2.BZ2File"><code class="xref py py-class docutils literal notranslate"><span class="pre">BZ2File</span></code></a>. If

  414. you need to decompress a multi-stream input with <a class="reference internal" href="#bz2.BZ2Decompressor" title="bz2.BZ2Decompressor"><code class="xref py py-class docutils literal notranslate"><span class="pre">BZ2Decompressor</span></code></a>,

  415. you must use a new decompressor for each stream.</p>

  416. </div>

  417. <dl class="py method">

  418. <dt class="sig sig-object py" id="bz2.BZ2Decompressor.decompress">

  419. <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="#bz2.BZ2Decompressor.decompress" title="Link to this definition">¶</a></dt>

  420. <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

  421. uncompressed data as bytes. Some of <em>data</em> may be buffered

  422. internally, for use in later calls to <a class="reference internal" href="#bz2.decompress" title="bz2.decompress"><code class="xref py py-meth docutils literal notranslate"><span class="pre">decompress()</span></code></a>. The

  423. returned data should be concatenated with the output of any

  424. previous calls to <a class="reference internal" href="#bz2.decompress" title="bz2.decompress"><code class="xref py py-meth docutils literal notranslate"><span class="pre">decompress()</span></code></a>.</p>

  425. <p>If <em>max_length</em> is nonnegative, returns at most <em>max_length</em>

  426. bytes of decompressed data. If this limit is reached and further

  427. output can be produced, the <a class="reference internal" href="#bz2.BZ2Decompressor.needs_input" title="bz2.BZ2Decompressor.needs_input"><code class="xref py py-attr docutils literal notranslate"><span class="pre">needs_input</span></code></a> attribute will

  428. be set to <code class="docutils literal notranslate"><span class="pre">False</span></code>. In this case, the next call to

  429. <a class="reference internal" href="#bz2.BZ2Decompressor.decompress" title="bz2.BZ2Decompressor.decompress"><code class="xref py py-meth docutils literal notranslate"><span class="pre">decompress()</span></code></a> may provide <em>data</em> as <code class="docutils literal notranslate"><span class="pre">b''</span></code> to obtain

  430. more of the output.</p>

  431. <p>If all of the input data was decompressed and returned (either

  432. because this was less than <em>max_length</em> bytes, or because

  433. <em>max_length</em> was negative), the <a class="reference internal" href="#bz2.BZ2Decompressor.needs_input" title="bz2.BZ2Decompressor.needs_input"><code class="xref py py-attr docutils literal notranslate"><span class="pre">needs_input</span></code></a> attribute

  434. will be set to <code class="docutils literal notranslate"><span class="pre">True</span></code>.</p>

  435. <p>Attempting to decompress data after the end of stream is reached

  436. raises an <a class="reference internal" href="exceptions.html#EOFError" title="EOFError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">EOFError</span></code></a>.  Any data found after the end of the

  437. stream is ignored and saved in the <a class="reference internal" href="#bz2.BZ2Decompressor.unused_data" title="bz2.BZ2Decompressor.unused_data"><code class="xref py py-attr docutils literal notranslate"><span class="pre">unused_data</span></code></a> attribute.</p>

  438. <div class="versionchanged">

  439. <p><span class="versionmodified changed">Changed in version 3.5: </span>Added the <em>max_length</em> parameter.</p>

  440. </div>

  441. </dd></dl>

  442. 

  443. <dl class="py attribute">

  444. <dt class="sig sig-object py" id="bz2.BZ2Decompressor.eof">

  445. <span class="sig-name descname"><span class="pre">eof</span></span><a class="headerlink" href="#bz2.BZ2Decompressor.eof" title="Link to this definition">¶</a></dt>

  446. <dd><p><code class="docutils literal notranslate"><span class="pre">True</span></code> if the end-of-stream marker has been reached.</p>

  447. <div class="versionadded">

  448. <p><span class="versionmodified added">New in version 3.3.</span></p>

  449. </div>

  450. </dd></dl>

  451. 

  452. <dl class="py attribute">

  453. <dt class="sig sig-object py" id="bz2.BZ2Decompressor.unused_data">

  454. <span class="sig-name descname"><span class="pre">unused_data</span></span><a class="headerlink" href="#bz2.BZ2Decompressor.unused_data" title="Link to this definition">¶</a></dt>

  455. <dd><p>Data found after the end of the compressed stream.</p>

  456. <p>If this attribute is accessed before the end of the stream has been

  457. reached, its value will be <code class="docutils literal notranslate"><span class="pre">b''</span></code>.</p>

  458. </dd></dl>

  459. 

  460. <dl class="py attribute">

  461. <dt class="sig sig-object py" id="bz2.BZ2Decompressor.needs_input">

  462. <span class="sig-name descname"><span class="pre">needs_input</span></span><a class="headerlink" href="#bz2.BZ2Decompressor.needs_input" title="Link to this definition">¶</a></dt>

  463. <dd><p><code class="docutils literal notranslate"><span class="pre">False</span></code> if the <a class="reference internal" href="#bz2.BZ2Decompressor.decompress" title="bz2.BZ2Decompressor.decompress"><code class="xref py py-meth docutils literal notranslate"><span class="pre">decompress()</span></code></a> method can provide more

  464. decompressed data before requiring new uncompressed input.</p>

  465. <div class="versionadded">

  466. <p><span class="versionmodified added">New in version 3.5.</span></p>

  467. </div>

  468. </dd></dl>

  469. 

  470. </dd></dl>

  471. 

  472. </section>

  473. <section id="one-shot-de-compression">

  474. <h2>One-shot (de)compression<a class="headerlink" href="#one-shot-de-compression" title="Link to this heading">¶</a></h2>

  475. <dl class="py function">

  476. <dt class="sig sig-object py" id="bz2.compress">

  477. <span class="sig-prename descclassname"><span class="pre">bz2.</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">compresslevel</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">9</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#bz2.compress" title="Link to this definition">¶</a></dt>

  478. <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>.</p>

  479. <p><em>compresslevel</em>, if given, must be an integer between <code class="docutils literal notranslate"><span class="pre">1</span></code> and <code class="docutils literal notranslate"><span class="pre">9</span></code>. The

  480. default is <code class="docutils literal notranslate"><span class="pre">9</span></code>.</p>

  481. <p>For incremental compression, use a <a class="reference internal" href="#bz2.BZ2Compressor" title="bz2.BZ2Compressor"><code class="xref py py-class docutils literal notranslate"><span class="pre">BZ2Compressor</span></code></a> instead.</p>

  482. </dd></dl>

  483. 

  484. <dl class="py function">

  485. <dt class="sig sig-object py" id="bz2.decompress">

  486. <span class="sig-prename descclassname"><span class="pre">bz2.</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><span class="sig-paren">)</span><a class="headerlink" href="#bz2.decompress" title="Link to this definition">¶</a></dt>

  487. <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>.</p>

  488. <p>If <em>data</em> is the concatenation of multiple compressed streams, decompress

  489. all of the streams.</p>

  490. <p>For incremental decompression, use a <a class="reference internal" href="#bz2.BZ2Decompressor" title="bz2.BZ2Decompressor"><code class="xref py py-class docutils literal notranslate"><span class="pre">BZ2Decompressor</span></code></a> instead.</p>

  491. <div class="versionchanged">

  492. <p><span class="versionmodified changed">Changed in version 3.3: </span>Support for multi-stream inputs was added.</p>

  493. </div>

  494. </dd></dl>

  495. 

  496. </section>

  497. <section id="examples-of-usage">

  498. <span id="bz2-usage-examples"></span><h2>Examples of usage<a class="headerlink" href="#examples-of-usage" title="Link to this heading">¶</a></h2>

  499. <p>Below are some examples of typical usage of the <a class="reference internal" href="#module-bz2" title="bz2: Interfaces for bzip2 compression and decompression."><code class="xref py py-mod docutils literal notranslate"><span class="pre">bz2</span></code></a> module.</p>

  500. <p>Using <a class="reference internal" href="#bz2.compress" title="bz2.compress"><code class="xref py py-func docutils literal notranslate"><span class="pre">compress()</span></code></a> and <a class="reference internal" href="#bz2.decompress" title="bz2.decompress"><code class="xref py py-func docutils literal notranslate"><span class="pre">decompress()</span></code></a> to demonstrate round-trip compression:</p>

  501. <div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="kn">import</span> <span class="nn">bz2</span>

  502. <span class="gp">&gt;&gt;&gt; </span><span class="n">data</span> <span class="o">=</span> <span class="sa">b</span><span class="s2">&quot;&quot;&quot;</span><span class="se">\</span>

  503. <span class="gp">... </span><span class="s2">Donec rhoncus quis sapien sit amet molestie. Fusce scelerisque vel augue</span>

  504. <span class="gp">... </span><span class="s2">nec ullamcorper. Nam rutrum pretium placerat. Aliquam vel tristique lorem,</span>

  505. <span class="gp">... </span><span class="s2">sit amet cursus ante. In interdum laoreet mi, sit amet ultrices purus</span>

  506. <span class="gp">... </span><span class="s2">pulvinar a. Nam gravida euismod magna, non varius justo tincidunt feugiat.</span>

  507. <span class="gp">... </span><span class="s2">Aliquam pharetra lacus non risus vehicula rutrum. Maecenas aliquam leo</span>

  508. <span class="gp">... </span><span class="s2">felis. Pellentesque semper nunc sit amet nibh ullamcorper, ac elementum</span>

  509. <span class="gp">... </span><span class="s2">dolor luctus. Curabitur lacinia mi ornare consectetur vestibulum.&quot;&quot;&quot;</span>

  510. <span class="gp">&gt;&gt;&gt; </span><span class="n">c</span> <span class="o">=</span> <span class="n">bz2</span><span class="o">.</span><span class="n">compress</span><span class="p">(</span><span class="n">data</span><span class="p">)</span>

  511. <span class="gp">&gt;&gt;&gt; </span><span class="nb">len</span><span class="p">(</span><span class="n">data</span><span class="p">)</span> <span class="o">/</span> <span class="nb">len</span><span class="p">(</span><span class="n">c</span><span class="p">)</span>  <span class="c1"># Data compression ratio</span>

  512. <span class="go">1.513595166163142</span>

  513. <span class="gp">&gt;&gt;&gt; </span><span class="n">d</span> <span class="o">=</span> <span class="n">bz2</span><span class="o">.</span><span class="n">decompress</span><span class="p">(</span><span class="n">c</span><span class="p">)</span>

  514. <span class="gp">&gt;&gt;&gt; </span><span class="n">data</span> <span class="o">==</span> <span class="n">d</span>  <span class="c1"># Check equality to original object after round-trip</span>

  515. <span class="go">True</span>

  516. </pre></div>

  517. </div>

  518. <p>Using <a class="reference internal" href="#bz2.BZ2Compressor" title="bz2.BZ2Compressor"><code class="xref py py-class docutils literal notranslate"><span class="pre">BZ2Compressor</span></code></a> for incremental compression:</p>

  519. <div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="kn">import</span> <span class="nn">bz2</span>

  520. <span class="gp">&gt;&gt;&gt; </span><span class="k">def</span> <span class="nf">gen_data</span><span class="p">(</span><span class="n">chunks</span><span class="o">=</span><span class="mi">10</span><span class="p">,</span> <span class="n">chunksize</span><span class="o">=</span><span class="mi">1000</span><span class="p">):</span>

  521. <span class="gp">... </span><span class="w">    </span><span class="sd">&quot;&quot;&quot;Yield incremental blocks of chunksize bytes.&quot;&quot;&quot;</span>

  522. <span class="gp">... </span>    <span class="k">for</span> <span class="n">_</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="n">chunks</span><span class="p">):</span>

  523. <span class="gp">... </span>        <span class="k">yield</span> <span class="sa">b</span><span class="s2">&quot;z&quot;</span> <span class="o">*</span> <span class="n">chunksize</span>

  524. <span class="gp">...</span>

  525. <span class="gp">&gt;&gt;&gt; </span><span class="n">comp</span> <span class="o">=</span> <span class="n">bz2</span><span class="o">.</span><span class="n">BZ2Compressor</span><span class="p">()</span>

  526. <span class="gp">&gt;&gt;&gt; </span><span class="n">out</span> <span class="o">=</span> <span class="sa">b</span><span class="s2">&quot;&quot;</span>

  527. <span class="gp">&gt;&gt;&gt; </span><span class="k">for</span> <span class="n">chunk</span> <span class="ow">in</span> <span class="n">gen_data</span><span class="p">():</span>

  528. <span class="gp">... </span>    <span class="c1"># Provide data to the compressor object</span>

  529. <span class="gp">... </span>    <span class="n">out</span> <span class="o">=</span> <span class="n">out</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="n">chunk</span><span class="p">)</span>

  530. <span class="gp">...</span>

  531. <span class="gp">&gt;&gt;&gt; </span><span class="c1"># Finish the compression process.  Call this once you have</span>

  532. <span class="gp">&gt;&gt;&gt; </span><span class="c1"># finished providing data to the compressor.</span>

  533. <span class="gp">&gt;&gt;&gt; </span><span class="n">out</span> <span class="o">=</span> <span class="n">out</span> <span class="o">+</span> <span class="n">comp</span><span class="o">.</span><span class="n">flush</span><span class="p">()</span>

  534. </pre></div>

  535. </div>

  536. <p>The example above uses a very “nonrandom” stream of data

  537. (a stream of <code class="docutils literal notranslate"><span class="pre">b&quot;z&quot;</span></code> chunks).  Random data tends to compress poorly,

  538. while ordered, repetitive data usually yields a high compression ratio.</p>

  539. <p>Writing and reading a bzip2-compressed file in binary mode:</p>

  540. <div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="kn">import</span> <span class="nn">bz2</span>

  541. <span class="gp">&gt;&gt;&gt; </span><span class="n">data</span> <span class="o">=</span> <span class="sa">b</span><span class="s2">&quot;&quot;&quot;</span><span class="se">\</span>

  542. <span class="gp">... </span><span class="s2">Donec rhoncus quis sapien sit amet molestie. Fusce scelerisque vel augue</span>

  543. <span class="gp">... </span><span class="s2">nec ullamcorper. Nam rutrum pretium placerat. Aliquam vel tristique lorem,</span>

  544. <span class="gp">... </span><span class="s2">sit amet cursus ante. In interdum laoreet mi, sit amet ultrices purus</span>

  545. <span class="gp">... </span><span class="s2">pulvinar a. Nam gravida euismod magna, non varius justo tincidunt feugiat.</span>

  546. <span class="gp">... </span><span class="s2">Aliquam pharetra lacus non risus vehicula rutrum. Maecenas aliquam leo</span>

  547. <span class="gp">... </span><span class="s2">felis. Pellentesque semper nunc sit amet nibh ullamcorper, ac elementum</span>

  548. <span class="gp">... </span><span class="s2">dolor luctus. Curabitur lacinia mi ornare consectetur vestibulum.&quot;&quot;&quot;</span>

  549. <span class="gp">&gt;&gt;&gt; </span><span class="k">with</span> <span class="n">bz2</span><span class="o">.</span><span class="n">open</span><span class="p">(</span><span class="s2">&quot;myfile.bz2&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>

  550. <span class="gp">... </span>    <span class="c1"># Write compressed data to file</span>

  551. <span class="gp">... </span>    <span class="n">unused</span> <span class="o">=</span> <span class="n">f</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="n">data</span><span class="p">)</span>

  552. <span class="gp">...</span>

  553. <span class="gp">&gt;&gt;&gt; </span><span class="k">with</span> <span class="n">bz2</span><span class="o">.</span><span class="n">open</span><span class="p">(</span><span class="s2">&quot;myfile.bz2&quot;</span><span class="p">,</span> <span class="s2">&quot;rb&quot;</span><span class="p">)</span> <span class="k">as</span> <span class="n">f</span><span class="p">:</span>

  554. <span class="gp">... </span>    <span class="c1"># Decompress data from file</span>

  555. <span class="gp">... </span>    <span class="n">content</span> <span class="o">=</span> <span class="n">f</span><span class="o">.</span><span class="n">read</span><span class="p">()</span>

  556. <span class="gp">...</span>

  557. <span class="gp">&gt;&gt;&gt; </span><span class="n">content</span> <span class="o">==</span> <span class="n">data</span>  <span class="c1"># Check equality to original object after round-trip</span>

  558. <span class="go">True</span>

  559. </pre></div>

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