My GUI lets the user play a crossword online using Flask. When it is used as a package and initialised through an executable (like the one defined in a setup.py in the entry points), it works fine. However, if I import it as a module and execute it from a python file like so —

import xpuz
xpuz.main()  # initialises the gui and stuff

— I get this issue, which I will explain through a series of steps:

1. A crossword is created (attempts to initialise the flask web app)

2. This opens a duplicate gui somehow??

3. Once I “exit” the GUI (it doesn’t really close), the web app actually starts

NOTE: Pressing “destroy” results in the duplicate GUI being destroyed.

Here is my implementation of the flask app (simplified):

from multiprocessing import Process

def run_app(**kwargs):
    global server
    # _app_process essentially just calls Flask.run
    server = Process(target=app_process, kwargs=kwargs)
    server.start()

def terminate():
    server.terminate()
    server.join()

I know the cause of this issue is somewhere in this code I have provided, and it probably has something to do with tkinter not being threadsafe or whatever, but I don’t have much of a clue how to fix it. I have tried making it a daemon and using the threading module, but to no avail. The weirdest thing is that this happens ONLY when I am running the package directly through a python script.

Any ideas?!