Circular import dependency in Python

Question

Let\'s say I have the following directory structure:

a\\
    __init__.py
    b\\
        __init__.py
        c\\
            __init__.py
            c_file.p         


        

Answer 1

The problem is that when running from a directory, by default only the packages that are sub directories are visible as candidate imports, so you cannot import a.b.d. You can however import b.d. since b is a sub package of a.

If you really want to import a.b.d in c/__init__.py you can accomplish this by changing the system path to be one directory above a and change the import in a/__init__.py to be import a.b.c.

Your a/__init__.py should look like this:

import sys
import os
# set sytem path to be directory above so that a can be a 
# package namespace
DIRECTORY_SCRIPT = os.path.dirname(os.path.realpath(__file__)) 
sys.path.insert(0,DIRECTORY_SCRIPT+"/..")
import a.b.c

An additional difficulty arises when you want to run modules in c as scripts. Here the packages a and b do not exist. You can hack the __int__.py in the c directory to point the sys.path to the top-level directory and then import __init__ in any modules inside c to be able to use the full path to import a.b.d. I doubt that it is good practice to import __init__.py but it has worked for my use cases.