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+:mod:`runpy` --- Locating and executing Python modules
+======================================================
+
+.. module:: runpy
+   :synopsis: Locate and run Python modules without importing them first.
+.. moduleauthor:: Nick Coghlan <ncoghlan@gmail.com>
+
+
+.. versionadded:: 2.5
+
+The :mod:`runpy` module is used to locate and run Python modules without
+importing them first. Its main use is to implement the :option:`-m` command line
+switch that allows scripts to be located using the Python module namespace
+rather than the filesystem.
+
+When executed as a script, the module effectively operates as follows::
+
+   del sys.argv[0]  # Remove the runpy module from the arguments
+   run_module(sys.argv[0], run_name="__main__", alter_sys=True)
+
+The :mod:`runpy` module provides a single function:
+
+
+.. function:: run_module(mod_name[, init_globals] [, run_name][, alter_sys])
+
+   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 PEP 302 for details) and then executed in a fresh module
+   namespace.
+
+   The optional dictionary argument *init_globals* may be used to pre-populate the
+   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 the ``run_module``
+   function.
+
+   The special global variables ``__name__``, ``__file__``, ``__loader__`` and
+   ``__builtins__`` are set in the globals dictionary before the module code is
+   executed.
+
+   ``__name__`` is set to *run_name* if this optional argument is supplied, and the
+   *mod_name* argument otherwise.
+
+   ``__loader__`` is set to the PEP 302 module loader used to retrieve the code for
+   the module (This loader may be a wrapper around the standard import mechanism).
+
+   ``__file__`` is set to the name provided by the module loader. If the loader
+   does not make filename information available, this variable is set to ``None``.
+
+   ``__builtins__`` is automatically initialised with a reference to the top level
+   namespace of the :mod:`__builtin__` module.
+
+   If the argument *alter_sys* is supplied and evaluates to ``True``, then
+   ``sys.argv[0]`` is updated with the value of ``__file__`` and
+   ``sys.modules[__name__]`` is updated with a new module object for the module
+   being executed. Note that neither ``sys.argv[0]`` nor ``sys.modules[__name__]``
+   are restored to their original values before the function returns -- if client
+   code needs these values preserved, it must either save them explicitly or
+   else avoid enabling the automatic alterations to :mod:`sys`.
+
+   Note that this manipulation of :mod:`sys` 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 :mod:`sys` module be left alone when invoking this
+   function from threaded code.
+
+
+.. seealso::
+
+   :pep:`338` - Executing modules as scripts
+      PEP written and  implemented by Nick Coghlan.
+