mysterious a and b behavior

gistfile1.txt

Contents of a.py:

#!/usr/bin/env python3
import b
foo = None
def main():
    global foo
    foo = 32
    print(f'in a, foo={foo}')
    b.b()

if __name__ == "__main__":
    main()
    
 Contents of b.py:
    
import a
def b():\
    print(f'in b, a.foo={a.foo}')


Outputs:

$ python
Python 3.13.5 (main, Jun 25 2025, 18:55:22) [GCC 14.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import a
>>> a.main()
in a, foo=32
in b, a.foo=32
>>> quit
$ ./a.py
in a, foo=32
in b, a.foo=None