Python - Doing absolute imports from a subfolder

Question

Hi,

Basically I'm asking the same question as this guy: http://stackoverflow.com/questions/72852/how-to-do-relative-imports-in-python

But no one gave him a correct answer. Given that you are inside a subfolder and you want to go up a directory and then into ANOTHER subfolder, doing what they suggested does not work (as the OP pointed out in his comments to their answers).

I know that you can do this by using sys.path, but I would prefer a cleaner method.

Example:

App
__init__.py
Package_A
--__init__.py
--Module_A.py
Package_B
--__init__.py
--Module_B.py

How would I import Module_A into Module_B?

Answer 1

If I'm reading correctly, in Python 2.5 or higher:

from ..Module_B import Module_B

I thought I was well-versed in Python but I had no idea that was possible in version 2.5.

Answer 2

If you are then importing Module_B in to App, you would

Module_B.py: import ModuleA

App.py (which also imports ModuleA which is now by default in your Pythonpath)

import Module_B.Module_B

Another alternative, is to update __init__.py (the one in Module_A/App folder) to:

import os
import sys
sys.path.extend('%s../' % os.getcwd())
import ModuleA

Another alternative, is to add your folder to the PYTHONPATH environment var.

Answer 3

main.py
setup.py
app/ ->
    __init__.py
    package_a/ ->
       __init__.py
       module_a.py
    package_b/ ->
       __init__.py
       module_b.py

1. You run python main.py.
2. main.py does: import app.package_a.module_a
3. module_a.py does import app.package_b.module_b

Alternatively 2 or 3 could use: from app.package_a import module_a

That will work as long as you have app in your PYTHONPATH. main.py could be anywhere then.

So you write a setup.py to copy (install) the whole app package and subpackages to the target system's python folders, and main.py to target system's script folders.