\section{\module{runpy} ---
         Locating and executing Python code.}

\declaremodule{standard}{runpy}		% standard library, in Python

\moduleauthor{Nick Coghlan}{ncoghlan@gmail.com}

\modulesynopsis{Functions to locate and execute Python code}

\versionadded{2.5}

The \module{runpy} module is used to locate and run Python modules
without importing them first. It's main use is to implement the -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:
\begin{verbatim}
    del sys.argv[0]
    run_module(sys.argv[0], run_name="__main__", as_script=True)
\end{verbatim}

The \module{runpy} module provides a single function:

\begin{funcdesc}{run_module}{mod_name\optional{, init_globals}
\optional{, run_name}\optional{, 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 \var{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 \code{__name__}, \code{__file__},
\code{__loader__} and \code{__builtins__} are set in the globals
dictionary before the module code is executed.

\code{__name__} is set to \var{run_name} if this optional argument is
supplied, and the original \var{mod_name} argument otherwise.

\code{__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).

\code{__file__} is set to the name provided by the module loader. If
the loader does not make filename information available, this
argument is set to \code{None}.

\code{__builtins__} is automatically initialised with a reference to
the top level namespace of the \module{__builtin__} module.

If the argument \var{alter_sys} is supplied and evaluates to
\code{True}, then \code{sys.argv[0]} is updated with the value of
\code{__file__} and \code{sys.modules[__name__]} is updated with a
temporary module object for the module being executed. The import
lock is used to prevent other threads from seeing the partially
initialised module object. Both \code{sys.argv[0]} and
\code{sys.modules[__name__]} are restored to their original values
before the function returns.
\end{funcdesc}