pythonmoduleparent

Is there a way to access parent modules of an imported module object?

I need to know if there is a way to access parent modules from submodules. If I import submodule:

from subprocess import types

I have types - is there some Python magic to get access to subprocess module from types? Something similar to this for classes ().__class__.__bases__[0].__subclasses__().

Solution

  • If you've accessed a module you can typically get to it from the sys.modules dictionary. Python doesn't keep "parent pointers" with names, particularly because the relationship is not one-to-one. For example, using your example:

    >>> from subprocess import types
>>> types
<module 'types' from '/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/types.pyc'>
>>> import sys
>>> sys.modules['subprocess']
<module 'subprocess' from '/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.pyc'>

    If you'll note the presence of types in the subprocess module is just an artifact of the import types statement in it. You just import types if you need that module.

    In fact, a future version of subprocess may not import types any more, and your code will break. You should only import the names that appear in the __all__ list of a module; consider other names as implementation details.

    So, for example:

    >>> import subprocess
>>> dir(subprocess)
['CalledProcessError', 'MAXFD', 'PIPE', 'Popen', 'STDOUT', '_PIPE_BUF', '__all__', '__builtins__', '__doc__',
 '__file__', '__name__', '__package__', '_active', '_cleanup', '_demo_posix', '_demo_windows', '_eintr_retry_call',
 '_has_poll', 'call', 'check_call', 'check_output', 'errno', 'fcntl', 'gc', 'list2cmdline', 'mswindows', 'os',
 'pickle', 'select', 'signal', 'sys', 'traceback', 'types']
>>> subprocess.__all__
['Popen', 'PIPE', 'STDOUT', 'call', 'check_call', 'check_output', 'CalledProcessError']

    You can see that most of the names visible in subprocess are just other top-level modules that it imports.