How to change the attribute of an instance from an another file?

Question

I am new to oop and I had a doubt. Suppose we are in the main file and had an instance of a class say bot and, bot.var = 5 How do I edit bot.var in an another file such that the changes are reflected in the main file as well? Thanks for the help.

main.py :

class Foo:
    ...


bar = Foo()
bar.var = 5
print(bar.var)

file.py :

from main import Foo


class EditFoo(Foo):
    def __init__(self) -> None:
        super().__init__()
        # What do I do from here
        # such that the edits here are reflected on the main.py file

Thanks for the help