How to properly use relative or absolute imports in Python modules?

Question

Usage of relative imports in Python has one drawback, you will not be able to run the modules as standalones anymore because you will get an exception: ValueError: Attempted relative import in non-package

# /test.py: just a sample file importing foo module
import foo
...

# /foo/foo.py:
from . import bar
...
if __name__ == "__main__":
   pass

# /foo/bar.py: a submodule of foo, used by foo.py
from . import foo
...
if __name__ == "__main__":
   pass

How should I modify the sample code in order to be able to execute all: test.py, foo.py and bar.py

I'm looking for a solution that works with python 2.6+ (including 3.x).

Answer 1

You could just start 'to run the modules as standalones' in a bit a different way:

Instead of:

python foo/bar.py

Use:

python -mfoo.bar

Of course, the foo/__init__.py file must be present.

Please also note, that you have a circular dependency between foo.py and bar.py – this won't work. I guess it is just a mistake in your example.

Update: it seems it also works perfectly well to use this as the first line of the foo/bar.py:

#!/usr/bin/python -mfoo.bar

Then you can execute the script directly in POSIX systems.