Is there a way to access parent modules in Python

python module parent
jcubic picture jcubic · Mar 13, 2011 · Viewed 14.8k times · Source

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__().

Answer

Nicholas Riley picture Nicholas Riley · Mar 13, 2011

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.

Related questions

python import module from parent package

I have the following directory structure foo/ __init__.py settings.py bar/ __init__.py myfile.py In myfile.py I have: import settings I get the following error: ImportError: No module named settings, why? How can I efectively import the …

Read More
Python importing a module from a parallel directory

How would I organize my python imports so that I can have a directory like this. project | \ | __init__.py | src | \ | __init__.py | classes.py | test \ __init__.py tests.py And then inside /project/test/tests.py be able to import …

Read More
How can I get a list of locally installed Python modules?

I would like to get a list of Python modules, which are in my Python installation (UNIX server). How can you get a list of Python modules installed in your computer?

Read More