Using the “exec()” command from a function inside an import, not affecting the main file's variables

Question

I am currently making a module which exports the local variables to a python readable file and imports it through exec, but I am unable to modify them without using returns (Which is the whole idea). The problem boils down to:

I have two files, a module (module.py) and a main (main.py). I want the module to be able to execute code inside the main:

#module.py
def foo():
    exec("b = a")

#main.py
from module import foo
a = 10
foo()
print(b)

Expected outcome

10

Actual outcome

NameError: name 'b' is not defined

Answer 1

You can use __main__

main.py:

from module import foo
import __main__
a = 10
__main__ = foo(__main__)
print(b)

module.py:

def foo(main):
    main.b = main.a
    return main