Continue executing function

Question

When closing an instance of the ChildWindow class, which was called from another instance of MainWindow, the code does not continue to be executed.

I noticed that only when the MainWindow instance is closed does it continue to run. In general, it has a cumulative property, so the number of times the ChildWindow closes the window, the continuation will be displayed.

I want the function to continue executing when the ChildWindow closes, without closing the main window. Here's my code:

from tkinter import *

class MainWindow():

    def __init__(self):
        self.root = Tk()
        
    def run(self):
        Button(self.root, text='click', command=lambda:self.open_child_window()).pack()
        self.root.mainloop()

    def open_child_window(self):
        A = ChildWindow()
        A.run()
        print("why i'm not write?")

class ChildWindow():

    def __init__(self):
        self.root = Toplevel()

    def run(self):
        self.root.mainloop()


A = MainWindow()
A.run()

It seems to me that this is due to the self.root.mainloop() loop, so I was looking for how to stop it, the .quit(), .destroy() methods do not help.

You shouldn't be calling `Tk()` more than once - that creates the entire GUI environment (with limitations on how those environments can interact with each other), not just a window. You want `Toplevel()` for that. — jasonharper, Feb 07 '23 at 14:52
@chepner, I ran into the same problem. Intended .mainloop() prevents further execution — chikibamboni, Feb 07 '23 at 15:05
You should be able to continue with calling `self.root.quit()` from a button for example. Anyway, there is `wait_window` or `wait_variable` for this taks but be aware of what it does. https://stackoverflow.com/questions/74370984/is-tkwait-wait-variable-wait-window-wait-visibility-broken — Thingamabobs, Feb 07 '23 at 15:11
As an aside: writing `lambda: x()` is like writing `[x][0]` - either way, just write `x` instead. `lambda` is for when the function needs to be adapted (i.e., change the parameters, by ignoring some of what is passed in or by calculating more things to pass). — Karl Knechtel, Feb 08 '23 at 03:06

relent95 · Accepted Answer · 2023-02-10T01:00:30.973

1

It's called a nested event loop or modal loop. Use the mainloop() and quit() like this.

class ChildWindow():
    def __init__(self):
        self.root = Toplevel()

    def run(self):
        win = self.root
        def on_close():
            win.destroy()
            win.quit()
        win.protocol('WM_DELETE_WINDOW', on_close)
        win.mainloop()
        print('end of the nested loop')
...

You can also use wait_window() and destroy() like this.(The former runs a nested event loop until the window is destroyed.)

class ChildWindow():
    ...
    def run(self):
        win = self.root
        def on_close():
            win.destroy()
        win.protocol('WM_DELETE_WINDOW', on_close)
        win.wait_window()

edited Feb 10 '23 at 01:00

answered Feb 08 '23 at 02:59

relent95

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I was already told about the `wait_window` method, but this method also works. Somehow I'm even surprised that it works, because I already tried it. But anyway, thanks :D – chikibamboni Feb 09 '23 at 16:53
apparently it's all about the `win.destroy` and `win.quit` methods, because I tried to use them separately... – chikibamboni Feb 09 '23 at 16:59
A solution using the ```wait_window()``` was added. Thanks. – relent95 Feb 10 '23 at 01:01

Continue executing function

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