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

I suggest the following pattern. Using it will allow auto-completion and type hinting to work properly.

cyclic_import_a.py

import playground.cyclic_import_b

class A(object):
    def __init__(self):
        pass

    def print_a(self):
        print('a')

if __name__ == '__main__':
    a = A()
    a.print_a()

    b = playground.cyclic_import_b.B(a)
    b.print_b()

cyclic_import_b.py

import playground.cyclic_import_a

class B(object):
    def __init__(self, a):
        self.a: playground.cyclic_import_a.A = a

    def print_b(self):
        print('b1-----------------')
        self.a.print_a()
        print('b2-----------------')

---

You cannot import classes A & B using this syntax

from playgroud.cyclic_import_a import A
from playground.cyclic_import_b import B

---

You cannot declare the type of parameter a in class B __ init __ method, but you can "cast" it this way:

def __init__(self, a):
    self.a: playground.cyclic_import_a.A = a