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diff --git a/Doc/library/runpy.rst b/Doc/library/runpy.rst new file mode 100644 index 0000000000..8846973e30 --- /dev/null +++ b/Doc/library/runpy.rst @@ -0,0 +1,71 @@ +: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. + |