python: globally reloading a module

I am making a pygame dialog and i have files that are like that:

window.py:

class Window():
    def set_size(self, size):
        self.size = size

main_window = Window()

dialogs.py:

from window import main_window
class Question():
    def __init__(self):
        # lots of initializing
        self.position = (main_window.size[0] / 2, main_window.size[1] / 2) # centering dialog

question = Question()

other files:

from window import main_window
from dialogs import question

# do something

The problem is that if i change the size of the main window in one of the other files, then the question dialog will no longer be centered, since question is already initialized with a different screen size. So, i want to make the set_size method reload the question module for all other files. How can i do this?

Thanks

via Chebli Mohamed