| Georg Brandl | 8ec7f65 | 2007-08-15 14:28:01 +0000 | [diff] [blame^] | 1 | :mod:`runpy` --- Locating and executing Python modules |
| 2 | ====================================================== |
| 3 | |
| 4 | .. module:: runpy |
| 5 | :synopsis: Locate and run Python modules without importing them first. |
| 6 | .. moduleauthor:: Nick Coghlan <ncoghlan@gmail.com> |
| 7 | |
| 8 | |
| 9 | .. versionadded:: 2.5 |
| 10 | |
| 11 | The :mod:`runpy` module is used to locate and run Python modules without |
| 12 | importing them first. Its main use is to implement the :option:`-m` command line |
| 13 | switch that allows scripts to be located using the Python module namespace |
| 14 | rather than the filesystem. |
| 15 | |
| 16 | When executed as a script, the module effectively operates as follows:: |
| 17 | |
| 18 | del sys.argv[0] # Remove the runpy module from the arguments |
| 19 | run_module(sys.argv[0], run_name="__main__", alter_sys=True) |
| 20 | |
| 21 | The :mod:`runpy` module provides a single function: |
| 22 | |
| 23 | |
| 24 | .. function:: run_module(mod_name[, init_globals] [, run_name][, alter_sys]) |
| 25 | |
| 26 | Execute the code of the specified module and return the resulting module globals |
| 27 | dictionary. The module's code is first located using the standard import |
| 28 | mechanism (refer to PEP 302 for details) and then executed in a fresh module |
| 29 | namespace. |
| 30 | |
| 31 | The optional dictionary argument *init_globals* may be used to pre-populate the |
| 32 | globals dictionary before the code is executed. The supplied dictionary will not |
| 33 | be modified. If any of the special global variables below are defined in the |
| 34 | supplied dictionary, those definitions are overridden by the ``run_module`` |
| 35 | function. |
| 36 | |
| 37 | The special global variables ``__name__``, ``__file__``, ``__loader__`` and |
| 38 | ``__builtins__`` are set in the globals dictionary before the module code is |
| 39 | executed. |
| 40 | |
| 41 | ``__name__`` is set to *run_name* if this optional argument is supplied, and the |
| 42 | *mod_name* argument otherwise. |
| 43 | |
| 44 | ``__loader__`` is set to the PEP 302 module loader used to retrieve the code for |
| 45 | the module (This loader may be a wrapper around the standard import mechanism). |
| 46 | |
| 47 | ``__file__`` is set to the name provided by the module loader. If the loader |
| 48 | does not make filename information available, this variable is set to ``None``. |
| 49 | |
| 50 | ``__builtins__`` is automatically initialised with a reference to the top level |
| 51 | namespace of the :mod:`__builtin__` module. |
| 52 | |
| 53 | If the argument *alter_sys* is supplied and evaluates to ``True``, then |
| 54 | ``sys.argv[0]`` is updated with the value of ``__file__`` and |
| 55 | ``sys.modules[__name__]`` is updated with a new module object for the module |
| 56 | being executed. Note that neither ``sys.argv[0]`` nor ``sys.modules[__name__]`` |
| 57 | are restored to their original values before the function returns - if client |
| 58 | code needs these values preserved, it must either save them explicitly or else |
| 59 | avoid enabling the automatic alterations to :mod:`sys`. |
| 60 | |
| 61 | Note that this manipulation of :mod:`sys` is not thread-safe. Other threads may |
| 62 | see the partially initialised module, as well as the altered list of arguments. |
| 63 | It is recommended that the :mod:`sys` module be left alone when invoking this |
| 64 | function from threaded code. |
| 65 | |
| 66 | |
| 67 | .. seealso:: |
| 68 | |
| 69 | :pep:`338` - Executing modules as scripts |
| 70 | PEP written and implemented by Nick Coghlan. |
| 71 | |