Import module from sibling package with absolute import

Question

How does one use absolute imports from a module of a sibling package?

Package file structure:

.
├── a
│   ├── __init__.py
│   └── modulea.py
├── b
│   ├── __init__.py
│   ├── moduleb.py
├── __init__.py
└── test.py

Files test.py and a/modulea.py:

from b.moduleb import f

if __name__ == '__main__':
    f()

File b/moduleb.py:

def f():
    print('hello')

This works:

% python test.py 
hello

This does not:

% python a/modulea.py 
Traceback (most recent call last):
  File "a/modulea.py", line 1, in <module>
    from b.moduleb import f
ImportError: No module named 'b'

As far as I can tell from the documentation it should work: http://docs.python.org/3.3/tutorial/modules.html#intra-package-references. Am I missing something?

Answer 1

You need an __init__.py in whatever . is.

Answer 2

Use python -ma.modulea.

Running python a/modulea.py adds a directory to sys.path instead of the parent (.).

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