runpy — Locating and executing Python modules¶Source code: Lib/runpy.py
The runpy module is used to locate and run Python modules without
importing them first. Its 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.
Note that this is not a sandbox module - all code is executed in the current process, and any side effects (such as cached imports of other modules) will remain in place after the functions have returned.
Furthermore, any functions and classes defined by the executed code are not
guaranteed to work correctly after a runpy function has returned.
If that limitation is not acceptable for a given use case, importlib
is likely to be a more suitable choice than this module.
The runpy module provides two functions:
runpy.run_module(mod_name, init_globals=None, run_name=None, alter_sys=False)¶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 mod_name argument should be an absolute module name.
If the module name refers to a package rather than a normal
module, then that package is imported and the __main__ submodule within
that package is then executed and the resulting module globals dictionary
returned.
The optional dictionary argument init_globals may be used to pre-populate
the module’s 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 run_module().
The special global variables __name__, __spec__, __file__,
__cached__, __loader__ and __package__ are set in the globals
dictionary before the module code is executed (Note that this is a
minimal set of variables - other variables may be set implicitly as an
interpreter implementation detail).
__name__ is set to run_name if this optional argument is not
None, to mod_name + '.__main__' if the named module is a
package and to the mod_name argument otherwise.
__spec__ will be set appropriately for the actually imported
module (that is, __spec__.name will always be mod_name or
mod_name + '.__main__, never run_name).
__file__, __cached__, __loader__ and __package__ are
set as normal based on the module spec.
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 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 sys module be left alone when
invoking this function from threaded code.
See also
The -m option offering equivalent functionality from the
command line.
Changed in version 3.1: Added ability to execute packages by looking for a __main__ submodule.
Changed in version 3.2: Added __cached__ global variable (see PEP 3147).
Changed in version 3.4: Updated to take advantage of the module spec feature added by
PEP 451. This allows __cached__ to be set correctly for modules
run this way, as well as ensuring the real module name is always
accessible as __spec__.name.
runpy.run_path(file_path, init_globals=None, run_name=None)¶Execute the code at the named filesystem location and return the resulting
module globals dictionary. As with a script name supplied to the CPython
command line, the supplied path may refer to a Python source file, a
compiled bytecode file or a valid sys.path entry containing a __main__
module (e.g. a zipfile containing a top-level __main__.py file).
For a simple script, the specified code is simply executed in a fresh
module namespace. For a valid sys.path entry (typically a zipfile or
directory), the entry is first added to the beginning of sys.path. The
function then looks for and executes a __main__ module using the
updated path. Note that there is no special protection against invoking
an existing __main__ entry located elsewhere on sys.path if
there is no such module at the specified location.
The optional dictionary argument init_globals may be used to pre-populate
the module’s 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 run_path().
The special global variables __name__, __spec__, __file__,
__cached__, __loader__ and __package__ are set in the globals
dictionary before the module code is executed (Note that this is a
minimal set of variables - other variables may be set implicitly as an
interpreter implementation detail).
__name__ is set to run_name if this optional argument is not
None and to '<run_path>' otherwise.
If the supplied path directly references a script file (whether as source
or as precompiled byte code), then __file__ will be set to the
supplied path, and __spec__, __cached__, __loader__ and
__package__ will all be set to None.
If the supplied path is a reference to a valid sys.path entry, then
__spec__ will be set appropriately for the imported __main__
module (that is, __spec__.name will always be __main__).
__file__, __cached__, __loader__ and __package__ will be
set as normal based on the module spec.
A number of alterations are also made to the sys module. Firstly,
sys.path may be altered as described above. sys.argv[0] is updated
with the value of file_path and sys.modules[__name__] is updated
with a temporary module object for the module being executed. All
modifications to items in sys are reverted before the function
returns.
Note that, unlike run_module(), the alterations made to sys
are not optional in this function as these adjustments are essential to
allowing the execution of sys.path entries. As the thread-safety
limitations still apply, use of this function in threaded code should be
either serialised with the import lock or delegated to a separate process.
See also
using-on-interface-options for equivalent functionality on the
command line (python path/to/script).
New in version 3.2.
Changed in version 3.4: Updated to take advantage of the module spec feature added by
PEP 451. This allows __cached__ to be set correctly in the
case where __main__ is imported from a valid sys.path entry rather
than being executed directly.
See also
using-on-general - CPython command line details
The importlib.import_module() function