Relative import problems in Python 3

Question

Python imports drive me crazy (my experience with python imports sometime doesn't correspond at all to idiom 'Explicit is better than implicit' :( ):

[app]
    start.py
        from package1 import module1
    [package1]
        __init__.py
            print('Init package1')
        module1.py
            print('Init package1.module1')
            from . import module2
        module2.py
            print('Init package1.module2')
            import sys, pprint
            pprint.pprint(sys.modules)
            from . import module1

I get:

vic@ubuntu:~/Desktop/app2$ python3 start.py 
Init package1
Init package1.module1
Init package1.module2
{'__main__': <module '__main__' from 'start.py'>,
 ...
 'package1': <module 'package1' from '/home/vic/Desktop/app2/package1/__init__.py'>,
 'package1.module1': <module 'package1.module1' from '/home/vic/Desktop/app2/package1/module1.py'>,
 'package1.module2': <module 'package1.module2' from '/home/vic/Desktop/app2/package1/module2.py'>,
 ...
Traceback (most recent call last):
  File "start.py", line 3, in <module>
    from package1 import module1
  File "/home/vic/Desktop/app2/package1/module1.py", line 3, in <module>
    from . import module2
  File "/home/vic/Desktop/app2/package1/module2.py", line 5, in <module>
    from . import module1
ImportError: cannot import name module1
vic@ubuntu:~/Desktop/app2$ 

import package1.module1 works, but i want to use from . import module1 because i want to make package1 portable for my other applications, that's why i want to use relative paths.

I am using python 3.

I need circular imports. A function in module1 asserts that one of its parameter is instance of a class defined in module2 and viceversa.

In other words:

sys.modules contains 'package1.module1': <module 'package1.module1' from '/home/vic/Desktop/app2/package1/module1.py'>. I want to get a reference to it in form from . import module1, but it tries to get a name, not a package like in case import package1.module1 (which works fine). I tried import .module1 as m1 - but that's a syntax error.

Also, from . import module2 in module1 works fine, but from . import module1 in module2 doesn't work...

UPDATE:

This hack works (but i am looking for the 'official' way):

print('Init package1.module2')

import sys, pprint
pprint.pprint(sys.modules)

#from . import module1
parent_module_name = __name__.rpartition('.')[0]
module1 = sys.modules[parent_module_name + '.module1']

Answer 1

A better solution for your problem is to put package1 in it's own separate package. Of course then it can't import package2, but then again if it is reusable, why would it?