<!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta charset="utf-8" /> <title>py_compile — Compile Python source files — Python 3.7.10 documentation</title> <link rel="stylesheet" href="../_static/pydoctheme.css" type="text/css" /> <link rel="stylesheet" href="../_static/pygments.css" type="text/css" /> <script type="text/javascript" id="documentation_options" data-url_root="../" src="../_static/documentation_options.js"></script> <script type="text/javascript" src="../_static/jquery.js"></script> <script type="text/javascript" src="../_static/underscore.js"></script> <script type="text/javascript" src="../_static/doctools.js"></script> <script type="text/javascript" src="../_static/language_data.js"></script> <script type="text/javascript" src="../_static/sidebar.js"></script> <link rel="search" type="application/opensearchdescription+xml" title="Search within Python 3.7.10 documentation" href="../_static/opensearch.xml"/> <link rel="author" title="About these documents" href="../about.html" /> <link rel="index" title="Index" href="../genindex.html" /> <link rel="search" title="Search" href="../search.html" /> <link rel="copyright" title="Copyright" href="../copyright.html" /> <link rel="next" title="compileall — Byte-compile Python libraries" href="compileall.html" /> <link rel="prev" title="pyclbr — Python module browser support" href="pyclbr.html" /> <link rel="shortcut icon" type="image/png" href="../_static/py.png" /> <link rel="canonical" href="https://docs.python.org/3/library/py_compile.html" /> <script type="text/javascript" src="../_static/copybutton.js"></script> <style> @media only screen { table.full-width-table { width: 100%; 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The source code is loaded from the file named <em>file</em>. The byte-code is written to <em>cfile</em>, which defaults to the <span class="target" id="index-1"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-3147"><strong>PEP 3147</strong></a>/<span class="target" id="index-2"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0488"><strong>PEP 488</strong></a> path, ending in <code class="docutils literal notranslate"><span class="pre">.pyc</span></code>. For example, if <em>file</em> is <code class="docutils literal notranslate"><span class="pre">/foo/bar/baz.py</span></code> <em>cfile</em> will default to <code class="docutils literal notranslate"><span class="pre">/foo/bar/__pycache__/baz.cpython-32.pyc</span></code> for Python 3.2. If <em>dfile</em> is specified, it is used as the name of the source file in error messages when instead of <em>file</em>. If <em>doraise</em> is true, a <a class="reference internal" href="#py_compile.PyCompileError" title="py_compile.PyCompileError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">PyCompileError</span></code></a> is raised when an error is encountered while compiling <em>file</em>. If <em>doraise</em> is false (the default), an error string is written to <code class="docutils literal notranslate"><span class="pre">sys.stderr</span></code>, but no exception is raised. This function returns the path to byte-compiled file, i.e. whatever <em>cfile</em> value was used.</p> <p>If the path that <em>cfile</em> becomes (either explicitly specified or computed) is a symlink or non-regular file, <a class="reference internal" href="exceptions.html#FileExistsError" title="FileExistsError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">FileExistsError</span></code></a> will be raised. This is to act as a warning that import will turn those paths into regular files if it is allowed to write byte-compiled files to those paths. This is a side-effect of import using file renaming to place the final byte-compiled file into place to prevent concurrent file writing issues.</p> <p><em>optimize</em> controls the optimization level and is passed to the built-in <a class="reference internal" href="functions.html#compile" title="compile"><code class="xref py py-func docutils literal notranslate"><span class="pre">compile()</span></code></a> function. The default of <code class="docutils literal notranslate"><span class="pre">-1</span></code> selects the optimization level of the current interpreter.</p> <p><em>invalidation_mode</em> should be a member of the <a class="reference internal" href="#py_compile.PycInvalidationMode" title="py_compile.PycInvalidationMode"><code class="xref py py-class docutils literal notranslate"><span class="pre">PycInvalidationMode</span></code></a> enum and controls how the generated bytecode cache is invalidated at runtime. The default is <a class="reference internal" href="#py_compile.PycInvalidationMode.CHECKED_HASH" title="py_compile.PycInvalidationMode.CHECKED_HASH"><code class="xref py py-attr docutils literal notranslate"><span class="pre">PycInvalidationMode.CHECKED_HASH</span></code></a> if the <span class="target" id="index-3"></span><code class="xref std std-envvar docutils literal notranslate"><span class="pre">SOURCE_DATE_EPOCH</span></code> environment variable is set, otherwise the default is <a class="reference internal" href="#py_compile.PycInvalidationMode.TIMESTAMP" title="py_compile.PycInvalidationMode.TIMESTAMP"><code class="xref py py-attr docutils literal notranslate"><span class="pre">PycInvalidationMode.TIMESTAMP</span></code></a>.</p> <div class="versionchanged"> <p><span class="versionmodified changed">Changed in version 3.2: </span>Changed default value of <em>cfile</em> to be <span class="target" id="index-4"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-3147"><strong>PEP 3147</strong></a>-compliant. Previous default was <em>file</em> + <code class="docutils literal notranslate"><span class="pre">'c'</span></code> (<code class="docutils literal notranslate"><span class="pre">'o'</span></code> if optimization was enabled). Also added the <em>optimize</em> parameter.</p> </div> <div class="versionchanged"> <p><span class="versionmodified changed">Changed in version 3.4: </span>Changed code to use <a class="reference internal" href="importlib.html#module-importlib" title="importlib: The implementation of the import machinery."><code class="xref py py-mod docutils literal notranslate"><span class="pre">importlib</span></code></a> for the byte-code cache file writing. This means file creation/writing semantics now match what <a class="reference internal" href="importlib.html#module-importlib" title="importlib: The implementation of the import machinery."><code class="xref py py-mod docutils literal notranslate"><span class="pre">importlib</span></code></a> does, e.g. permissions, write-and-move semantics, etc. Also added the caveat that <a class="reference internal" href="exceptions.html#FileExistsError" title="FileExistsError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">FileExistsError</span></code></a> is raised if <em>cfile</em> is a symlink or non-regular file.</p> </div> <div class="versionchanged"> <p><span class="versionmodified changed">Changed in version 3.7: </span>The <em>invalidation_mode</em> parameter was added as specified in <span class="target" id="index-5"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0552"><strong>PEP 552</strong></a>. If the <span class="target" id="index-6"></span><code class="xref std std-envvar docutils literal notranslate"><span class="pre">SOURCE_DATE_EPOCH</span></code> environment variable is set, <em>invalidation_mode</em> will be forced to <a class="reference internal" href="#py_compile.PycInvalidationMode.CHECKED_HASH" title="py_compile.PycInvalidationMode.CHECKED_HASH"><code class="xref py py-attr docutils literal notranslate"><span class="pre">PycInvalidationMode.CHECKED_HASH</span></code></a>.</p> </div> <div class="versionchanged"> <p><span class="versionmodified changed">Changed in version 3.7.2: </span>The <span class="target" id="index-7"></span><code class="xref std std-envvar docutils literal notranslate"><span class="pre">SOURCE_DATE_EPOCH</span></code> environment variable no longer overrides the value of the <em>invalidation_mode</em> argument, and determines its default value instead.</p> </div> </dd></dl> <dl class="class"> <dt id="py_compile.PycInvalidationMode"> <em class="property">class </em><code class="sig-prename descclassname">py_compile.</code><code class="sig-name descname">PycInvalidationMode</code><a class="headerlink" href="#py_compile.PycInvalidationMode" title="Permalink to this definition">¶</a></dt> <dd><p>A enumeration of possible methods the interpreter can use to determine whether a bytecode file is up to date with a source file. The <code class="docutils literal notranslate"><span class="pre">.pyc</span></code> file indicates the desired invalidation mode in its header. See <a class="reference internal" href="../reference/import.html#pyc-invalidation"><span class="std std-ref">Cached bytecode invalidation</span></a> for more information on how Python invalidates <code class="docutils literal notranslate"><span class="pre">.pyc</span></code> files at runtime.</p> <div class="versionadded"> <p><span class="versionmodified added">New in version 3.7.</span></p> </div> <dl class="attribute"> <dt id="py_compile.PycInvalidationMode.TIMESTAMP"> <code class="sig-name descname">TIMESTAMP</code><a class="headerlink" href="#py_compile.PycInvalidationMode.TIMESTAMP" title="Permalink to this definition">¶</a></dt> <dd><p>The <code class="docutils literal notranslate"><span class="pre">.pyc</span></code> file includes the timestamp and size of the source file, which Python will compare against the metadata of the source file at runtime to determine if the <code class="docutils literal notranslate"><span class="pre">.pyc</span></code> file needs to be regenerated.</p> </dd></dl> <dl class="attribute"> <dt id="py_compile.PycInvalidationMode.CHECKED_HASH"> <code class="sig-name descname">CHECKED_HASH</code><a class="headerlink" href="#py_compile.PycInvalidationMode.CHECKED_HASH" title="Permalink to this definition">¶</a></dt> <dd><p>The <code class="docutils literal notranslate"><span class="pre">.pyc</span></code> file includes a hash of the source file content, which Python will compare against the source at runtime to determine if the <code class="docutils literal notranslate"><span class="pre">.pyc</span></code> file needs to be regenerated.</p> </dd></dl> <dl class="attribute"> <dt id="py_compile.PycInvalidationMode.UNCHECKED_HASH"> <code class="sig-name descname">UNCHECKED_HASH</code><a class="headerlink" href="#py_compile.PycInvalidationMode.UNCHECKED_HASH" title="Permalink to this definition">¶</a></dt> <dd><p>Like <a class="reference internal" href="#py_compile.PycInvalidationMode.CHECKED_HASH" title="py_compile.PycInvalidationMode.CHECKED_HASH"><code class="xref py py-attr docutils literal notranslate"><span class="pre">CHECKED_HASH</span></code></a>, the <code class="docutils literal notranslate"><span class="pre">.pyc</span></code> file includes a hash of the source file content. However, Python will at runtime assume the <code class="docutils literal notranslate"><span class="pre">.pyc</span></code> file is up to date and not validate the <code class="docutils literal notranslate"><span class="pre">.pyc</span></code> against the source file at all.</p> <p>This option is useful when the <code class="docutils literal notranslate"><span class="pre">.pycs</span></code> are kept up to date by some system external to Python like a build system.</p> </dd></dl> </dd></dl> <dl class="function"> <dt id="py_compile.main"> <code class="sig-prename descclassname">py_compile.</code><code class="sig-name descname">main</code><span class="sig-paren">(</span><em class="sig-param">args=None</em><span class="sig-paren">)</span><a class="headerlink" href="#py_compile.main" title="Permalink to this definition">¶</a></dt> <dd><p>Compile several source files. The files named in <em>args</em> (or on the command line, if <em>args</em> is <code class="docutils literal notranslate"><span class="pre">None</span></code>) are compiled and the resulting byte-code is cached in the normal manner. This function does not search a directory structure to locate source files; it only compiles files named explicitly. If <code class="docutils literal notranslate"><span class="pre">'-'</span></code> is the only parameter in args, the list of files is taken from standard input.</p> <div class="versionchanged"> <p><span class="versionmodified changed">Changed in version 3.2: </span>Added support for <code class="docutils literal notranslate"><span class="pre">'-'</span></code>.</p> </div> </dd></dl> <p>When this module is run as a script, the <a class="reference internal" href="#py_compile.main" title="py_compile.main"><code class="xref py py-func docutils literal notranslate"><span class="pre">main()</span></code></a> is used to compile all the files named on the command line. The exit status is nonzero if one of the files could not be compiled.</p> <div class="admonition seealso"> <p class="admonition-title">See also</p> <dl class="simple"> <dt>Module <a class="reference internal" href="compileall.html#module-compileall" title="compileall: Tools for byte-compiling all Python source files in a directory tree."><code class="xref py py-mod docutils literal notranslate"><span class="pre">compileall</span></code></a></dt><dd><p>Utilities to compile all Python source files in a directory tree.</p> </dd> </dl> </div> </div> </div> </div> </div> <div class="sphinxsidebar" role="navigation" aria-label="main navigation"> <div class="sphinxsidebarwrapper"> <h4>Previous topic</h4> <p class="topless"><a href="pyclbr.html" title="previous chapter"><code class="xref py py-mod docutils literal notranslate"><span class="pre">pyclbr</span></code> — Python module browser support</a></p> <h4>Next topic</h4> <p class="topless"><a href="compileall.html" title="next chapter"><code class="xref py py-mod docutils literal notranslate"><span class="pre">compileall</span></code> — Byte-compile Python libraries</a></p> <div role="note" aria-label="source link"> <h3>This Page</h3> <ul class="this-page-menu"> <li><a href="../bugs.html">Report a Bug</a></li> <li> <a href="https://github.com/python/cpython/blob/3.7/Doc/library/py_compile.rst" rel="nofollow">Show Source </a> </li> </ul> </div> </div> </div> <div class="clearer"></div> </div> <div class="related" role="navigation" aria-label="related navigation"> <h3>Navigation</h3> <ul> <li class="right" style="margin-right: 10px"> <a href="../genindex.html" title="General Index" >index</a></li> <li class="right" > <a href="../py-modindex.html" title="Python Module Index" >modules</a> |</li> <li class="right" > <a href="compileall.html" title="compileall — Byte-compile Python libraries" >next</a> |</li> <li class="right" > <a href="pyclbr.html" title="pyclbr — Python module browser support" >previous</a> |</li> <li><img src="../_static/py.png" alt="" style="vertical-align: middle; margin-top: -1px"/></li> <li><a href="https://www.python.org/">Python</a> »</li> <li> <a href="../index.html">3.7.10 Documentation</a> » </li> <li class="nav-item nav-item-1"><a href="index.html" >The Python Standard Library</a> »</li> <li class="nav-item nav-item-2"><a href="language.html" >Python Language Services</a> »</li> <li class="right"> <div class="inline-search" style="display: none" role="search"> <form class="inline-search" action="../search.html" method="get"> <input placeholder="Quick search" type="text" name="q" /> <input type="submit" value="Go" /> <input type="hidden" name="check_keywords" value="yes" /> <input type="hidden" name="area" value="default" /> </form> </div> <script type="text/javascript">$('.inline-search').show(0);</script> | </li> </ul> </div> <div class="footer"> © <a href="../copyright.html">Copyright</a> 2001-2021, Python Software Foundation. <br /> The Python Software Foundation is a non-profit corporation. <a href="https://www.python.org/psf/donations/">Please donate.</a> <br /> Last updated on Feb 26, 2021. <a href="../bugs.html">Found a bug</a>? <br /> Created using <a href="http://sphinx.pocoo.org/">Sphinx</a> 2.3.1. </div> </body> </html>