Unable to see changes to a global variable from a different Python module

Question

Consider the following Python application of two files, namely app.py:

#!/usr/bin/env python3
import other


MY_DICT = {'initial': 10}


def main():
    print('before main:', MY_DICT)
    MY_DICT['foo'] = 20
    MY_DICT['bar'] = 30
    print('after changes:', MY_DICT)
    other.check_dict()
    print('back in main:', MY_DICT)


if __name__ == '__main__':
    main()

and other.py:

def check_dict():
    from app import MY_DICT
    print('inside other:', MY_DICT)

I would like to make MY_DICT from app.py visible in other.py. It is visible, but I cannot change it. Here is the output if I run ./app.py with Python 3.8.0:

before main: {'initial': 10}
after changes: {'initial': 10, 'foo': 20, 'bar': 30}
inside other: {'initial': 10}
back in main: {'initial': 10, 'foo': 20, 'bar': 30}

Not only MY_DICT is back to its initial state when inspected from other.py, it's back to the changed state when I return to main.py. What is happening here and how do I make it the a real global variable?

I've already read this question and ensured that I do re-import MY_DICT in check_dict.