| :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> |
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| .. versionadded:: 2.5 |
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| 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. |
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| .. seealso:: |
| |
| :pep:`338` - Executing modules as scripts |
| PEP written and implemented by Nick Coghlan. |
| |