How to write a python package

Question

I am trying to refactor my code (a bunch of core modules and some apps living in a common directory). I want to get this structure

Root
   __init__.py
   Core
       __init__.py
       a.py
       b.py
       c.py
   AppOne
       __init__.py
       AppOne.py
   AppTwo
       __init__.py
       AppTwo.py
   AppThree
       __init__.py
       AppThree.py

where AppOne.py, AppTwo.py and AppThree.py imports the modules a, b and c in the Core package.

I don't understand how to write the __init__.py files and the import statements. I have read http://docs.python.org/tutorial/modules.html and http://guide.python-distribute.org/creation.html. I got errors like "Attempted relative import in non-package" or "Invalid Sintaxis"

you can leave them (the __init__.py) empty and it will work. you only need to put something there if you have particular special requirements (ie want to hide things). — andrew cooke
– andrew cooke, Commented May 17, 2012 at 22:43

sarveshseri · Accepted Answer · 2012-05-17 22:53:02Z

5

You need to add the directory of the python modules to sys path.

If you have something like this

Root
   here_using_my_module.py
   my_module
       __init__.py  --> leave it empty
       a.py
       b.py
       c.py

You need to add you module directory to sys_path

//here_using_your_module.py
import os, sys

abspath = lambda *p: os.path.abspath(os.path.join(*p))

PROJECT_ROOT = abspath(os.path.dirname(__file__))

sys.path.insert(0,PROJECT_ROOT)

import a from my_module

a.do_something()

answered May 17, 2012 at 22:53

sarveshseri

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1 Comment

Daniel Walther Berns Over a year ago

This is the point! Thank you very much. I had forgotten to update sys.path.

joemar.ct · Accepted Answer · 2012-05-17 22:54:30Z

1

Within AppOne.py:

import os
os.chdir("..")

from Core import a

alternatively, you may write in AppOne.py:

import sys
sys.path.insert(-1,"..")

from Core import a

answered May 17, 2012 at 22:54

joemar.ct

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Comments

Blender · Accepted Answer · 2012-05-18 00:40:33Z

1

If you have that exact directory structure, you can use relative imports to import from the parent folder:

from ..Core import a

answered May 18, 2012 at 0:40

Blender

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