===== root/one.py =====

from root import two

class One:

    def thing(self):
        print(two.Two())

===== root/two.py =====

from root import one

class Two:

    def thing(self):
        print(one.One())

===== root/__init__.py =====


===== REPL session =====

$ python3
Python 3.11.2 (main, Mar 13 2023, 12:18:29) [GCC 12.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from root import one
>>> one.One().thing()
<root.two.Two object at 0x7f284b0aead0>
>>> from root import two
>>> two.Two().thing()
<root.one.One object at 0x7f284b0aea10>