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<div class="section" id="module-runpy">
<span id="runpy-locating-and-executing-python-modules"></span><h1>31.7. <a class="reference internal" href="#module-runpy" title="runpy: Locate and run Python modules without importing them first."><code class="xref py py-mod docutils literal notranslate"><span class="pre">runpy</span></code></a> — Locating and executing Python modules<a class="headerlink" href="#module-runpy" title="Permalink to this headline">¶</a></h1>
<div class="versionadded">
<p><span class="versionmodified added">New in version 2.5.</span></p>
</div>
<p><strong>Source code:</strong> <a class="reference external" href="https://github.com/python/cpython/tree/2.7/Lib/runpy.py">Lib/runpy.py</a></p>
<hr class="docutils" />
<p>The <a class="reference internal" href="#module-runpy" title="runpy: Locate and run Python modules without importing them first."><code class="xref py py-mod docutils literal notranslate"><span class="pre">runpy</span></code></a> module is used to locate and run Python modules without
importing them first. Its main use is to implement the <a class="reference internal" href="../using/cmdline.html#cmdoption-m"><code class="xref std std-option docutils literal notranslate"><span class="pre">-m</span></code></a> command
line switch that allows scripts to be located using the Python module
namespace rather than the filesystem.</p>
<p>The <a class="reference internal" href="#module-runpy" title="runpy: Locate and run Python modules without importing them first."><code class="xref py py-mod docutils literal notranslate"><span class="pre">runpy</span></code></a> module provides two functions:</p>
<dl class="function">
<dt id="runpy.run_module">
<code class="descclassname">runpy.</code><code class="descname">run_module</code><span class="sig-paren">(</span><em>mod_name</em>, <em>init_globals=None</em>, <em>run_name=None</em>, <em>alter_sys=False</em><span class="sig-paren">)</span><a class="headerlink" href="#runpy.run_module" title="Permalink to this definition">¶</a></dt>
<dd><p id="index-0">Execute the code of the specified module and return the resulting module
globals dictionary. The module’s code is first located using the standard
import mechanism (refer to <span class="target" id="index-1"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0302"><strong>PEP 302</strong></a> for details) and then executed in a
fresh module namespace.</p>
<p>If the supplied module name refers to a package rather than a normal
module, then that package is imported and the <code class="docutils literal notranslate"><span class="pre">__main__</span></code> submodule within
that package is then executed and the resulting module globals dictionary
returned.</p>
<p>The optional dictionary argument <em>init_globals</em> may be used to pre-populate
the module’s globals dictionary before the code is executed. The supplied
dictionary will not be modified. If any of the special global variables
below are defined in the supplied dictionary, those definitions are
overridden by <a class="reference internal" href="#runpy.run_module" title="runpy.run_module"><code class="xref py py-func docutils literal notranslate"><span class="pre">run_module()</span></code></a>.</p>
<p>The special global variables <code class="docutils literal notranslate"><span class="pre">__name__</span></code>, <code class="docutils literal notranslate"><span class="pre">__file__</span></code>, <code class="docutils literal notranslate"><span class="pre">__loader__</span></code>
and <code class="docutils literal notranslate"><span class="pre">__package__</span></code> are set in the globals dictionary before the module
code is executed (Note that this is a minimal set of variables - other
variables may be set implicitly as an interpreter implementation detail).</p>
<p><code class="docutils literal notranslate"><span class="pre">__name__</span></code> is set to <em>run_name</em> if this optional argument is not
<a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal notranslate"><span class="pre">None</span></code></a>, to <code class="docutils literal notranslate"><span class="pre">mod_name</span> <span class="pre">+</span> <span class="pre">'.__main__'</span></code> if the named module is a
package and to the <em>mod_name</em> argument otherwise.</p>
<p><code class="docutils literal notranslate"><span class="pre">__file__</span></code> is set to the name provided by the module loader. If the
loader does not make filename information available, this variable is set
to <a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal notranslate"><span class="pre">None</span></code></a>.</p>
<p><code class="docutils literal notranslate"><span class="pre">__loader__</span></code> is set to the <span class="target" id="index-2"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0302"><strong>PEP 302</strong></a> module loader used to retrieve the
code for the module (This loader may be a wrapper around the standard
import mechanism).</p>
<p><code class="docutils literal notranslate"><span class="pre">__package__</span></code> is set to <em>mod_name</em> if the named module is a package and
to <code class="docutils literal notranslate"><span class="pre">mod_name.rpartition('.')[0]</span></code> otherwise.</p>
<p>If the argument <em>alter_sys</em> is supplied and evaluates to <a class="reference internal" href="constants.html#True" title="True"><code class="xref py py-const docutils literal notranslate"><span class="pre">True</span></code></a>,
then <code class="docutils literal notranslate"><span class="pre">sys.argv[0]</span></code> is updated with the value of <code class="docutils literal notranslate"><span class="pre">__file__</span></code> and
<code class="docutils literal notranslate"><span class="pre">sys.modules[__name__]</span></code> is updated with a temporary module object for the
module being executed. Both <code class="docutils literal notranslate"><span class="pre">sys.argv[0]</span></code> and <code class="docutils literal notranslate"><span class="pre">sys.modules[__name__]</span></code>
are restored to their original values before the function returns.</p>
<p>Note that this manipulation of <a class="reference internal" href="sys.html#module-sys" title="sys: Access system-specific parameters and functions."><code class="xref py py-mod docutils literal notranslate"><span class="pre">sys</span></code></a> is not thread-safe. Other threads
may see the partially initialised module, as well as the altered list of
arguments. It is recommended that the <a class="reference internal" href="sys.html#module-sys" title="sys: Access system-specific parameters and functions."><code class="xref py py-mod docutils literal notranslate"><span class="pre">sys</span></code></a> module be left alone when
invoking this function from threaded code.</p>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<p>The <a class="reference internal" href="../using/cmdline.html#cmdoption-m"><code class="xref std std-option docutils literal notranslate"><span class="pre">-m</span></code></a> option offering equivalent functionality from the
command line.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 2.7: </span>Added ability to execute packages by looking for a <code class="docutils literal notranslate"><span class="pre">__main__</span></code>
submodule</p>
</div>
</dd></dl>
<dl class="function">
<dt id="runpy.run_path">
<code class="descclassname">runpy.</code><code class="descname">run_path</code><span class="sig-paren">(</span><em>file_path</em>, <em>init_globals=None</em>, <em>run_name=None</em><span class="sig-paren">)</span><a class="headerlink" href="#runpy.run_path" title="Permalink to this definition">¶</a></dt>
<dd><p id="index-3">Execute the code at the named filesystem location and return the resulting
module globals dictionary. As with a script name supplied to the CPython
command line, the supplied path may refer to a Python source file, a
compiled bytecode file or a valid sys.path entry containing a <code class="docutils literal notranslate"><span class="pre">__main__</span></code>
module (e.g. a zipfile containing a top-level <code class="docutils literal notranslate"><span class="pre">__main__.py</span></code> file).</p>
<p>For a simple script, the specified code is simply executed in a fresh
module namespace. For a valid sys.path entry (typically a zipfile or
directory), the entry is first added to the beginning of <code class="docutils literal notranslate"><span class="pre">sys.path</span></code>. The
function then looks for and executes a <a class="reference internal" href="__main__.html#module-__main__" title="__main__: The environment where the top-level script is run."><code class="xref py py-mod docutils literal notranslate"><span class="pre">__main__</span></code></a> module using the
updated path. Note that there is no special protection against invoking
an existing <a class="reference internal" href="__main__.html#module-__main__" title="__main__: The environment where the top-level script is run."><code class="xref py py-mod docutils literal notranslate"><span class="pre">__main__</span></code></a> entry located elsewhere on <code class="docutils literal notranslate"><span class="pre">sys.path</span></code> if
there is no such module at the specified location.</p>
<p>The optional dictionary argument <em>init_globals</em> may be used to pre-populate
the module’s globals dictionary before the code is executed. The supplied
dictionary will not be modified. If any of the special global variables
below are defined in the supplied dictionary, those definitions are
overridden by <a class="reference internal" href="#runpy.run_path" title="runpy.run_path"><code class="xref py py-func docutils literal notranslate"><span class="pre">run_path()</span></code></a>.</p>
<p>The special global variables <code class="docutils literal notranslate"><span class="pre">__name__</span></code>, <code class="docutils literal notranslate"><span class="pre">__file__</span></code>, <code class="docutils literal notranslate"><span class="pre">__loader__</span></code>
and <code class="docutils literal notranslate"><span class="pre">__package__</span></code> are set in the globals dictionary before the module
code is executed (Note that this is a minimal set of variables - other
variables may be set implicitly as an interpreter implementation detail).</p>
<p><code class="docutils literal notranslate"><span class="pre">__name__</span></code> is set to <em>run_name</em> if this optional argument is not
<a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal notranslate"><span class="pre">None</span></code></a> and to <code class="docutils literal notranslate"><span class="pre">'<run_path>'</span></code> otherwise.</p>
<p><code class="docutils literal notranslate"><span class="pre">__file__</span></code> is set to the name provided by the module loader. If the
loader does not make filename information available, this variable is set
to <a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal notranslate"><span class="pre">None</span></code></a>. For a simple script, this will be set to <code class="docutils literal notranslate"><span class="pre">file_path</span></code>.</p>
<p><code class="docutils literal notranslate"><span class="pre">__loader__</span></code> is set to the <span class="target" id="index-4"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0302"><strong>PEP 302</strong></a> module loader used to retrieve the
code for the module (This loader may be a wrapper around the standard
import mechanism). For a simple script, this will be set to <a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal notranslate"><span class="pre">None</span></code></a>.</p>
<p><code class="docutils literal notranslate"><span class="pre">__package__</span></code> is set to <code class="docutils literal notranslate"><span class="pre">__name__.rpartition('.')[0]</span></code>.</p>
<p>A number of alterations are also made to the <a class="reference internal" href="sys.html#module-sys" title="sys: Access system-specific parameters and functions."><code class="xref py py-mod docutils literal notranslate"><span class="pre">sys</span></code></a> module. Firstly,
<code class="docutils literal notranslate"><span class="pre">sys.path</span></code> may be altered as described above. <code class="docutils literal notranslate"><span class="pre">sys.argv[0]</span></code> is updated
with the value of <code class="docutils literal notranslate"><span class="pre">file_path</span></code> and <code class="docutils literal notranslate"><span class="pre">sys.modules[__name__]</span></code> is updated
with a temporary module object for the module being executed. All
modifications to items in <a class="reference internal" href="sys.html#module-sys" title="sys: Access system-specific parameters and functions."><code class="xref py py-mod docutils literal notranslate"><span class="pre">sys</span></code></a> are reverted before the function
returns.</p>
<p>Note that, unlike <a class="reference internal" href="#runpy.run_module" title="runpy.run_module"><code class="xref py py-func docutils literal notranslate"><span class="pre">run_module()</span></code></a>, the alterations made to <a class="reference internal" href="sys.html#module-sys" title="sys: Access system-specific parameters and functions."><code class="xref py py-mod docutils literal notranslate"><span class="pre">sys</span></code></a>
are not optional in this function as these adjustments are essential to
allowing the execution of sys.path entries. As the thread-safety
limitations still apply, use of this function in threaded code should be
either serialised with the import lock or delegated to a separate process.</p>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<p><a class="reference internal" href="../using/cmdline.html#using-on-interface-options"><span class="std std-ref">Interface options</span></a> for equivalent functionality on the
command line (<code class="docutils literal notranslate"><span class="pre">python</span> <span class="pre">path/to/script</span></code>).</p>
</div>
<div class="versionadded">
<p><span class="versionmodified added">New in version 2.7.</span></p>
</div>
</dd></dl>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<dl class="simple">
<dt><span class="target" id="index-5"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0338"><strong>PEP 338</strong></a> – Executing modules as scripts</dt><dd><p>PEP written and implemented by Nick Coghlan.</p>
</dd>
<dt><span class="target" id="index-6"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0366"><strong>PEP 366</strong></a> – Main module explicit relative imports</dt><dd><p>PEP written and implemented by Nick Coghlan.</p>
</dd>
</dl>
<p><a class="reference internal" href="../using/cmdline.html#using-on-general"><span class="std std-ref">Command line and environment</span></a> - CPython command line details</p>
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