execute python code after window is closed.

Describe the problem I want to run one/two python code after my GUI gets closed.

I already use a location.realod() function in some places, which is why i cant use js (beforeunload). Therefore I wanted to know at which point in the project I would have to put my python code. I have a while loop for eel.sleep. But when I close and try to print something afterwards it doesnt happen. I assume it would have to go in another place

def main():
    app = App()
    app.mainloop()
    print("Hello world")
if __name__ == '__main__':
    main()