/Doc/library/runpy.rst
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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 temporary module object for the
- module being executed. Both ``sys.argv[0]`` and ``sys.modules[__name__]``
- are restored to their original values before the function returns.
- 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.