passing arguments in tkinter's protocol("WM_DELETE_WINDOW") function on python

Question

I am trying to create a simple python program with one thread handling UI and another “Background stuff”. I'd like to run a function when the user tries to exit my application a dialogue choice appears.

When I run the following code the function “on_closing()” runs automatically. As I understand I have to pass the function name only in the protocol function but I need a couple of arguments.

class MainWindow:

    def __init__(self, master):

        master.resizable(0, 0)
        master.protocol("WM_DELETE_WINDOW", self.on_closing(master))
        do_stuff('...')

    def on_closing(self, master):
        do_stuff('...')
        self.Destroy(master)

def call_window_manager(title):
    do_stuff(title)
    root = Tk()
    mw = MainWindow(root)
    root.mainloop()


def call_tools(title, mainwindow, master):
    do_stuff(title)


if __name__ == '__main__':

    do_stuff('main line')

    p1 = mp.Process(target=call_window_manager, args=('Window Manager Thread',))
    p2 = mp.Process(target=call_tools, args=('Tools Thread',))

    p1.start()
    p2.start()
    p1.join()
    p2.join()

How do I pass arguments then? Am I approaching this with the wrong way?

Ps: what’s the best way to terminate the other thread at the same time?

Nae · Accepted Answer · 2018-03-11 14:01:45Z

3

You can pass arguments to protocol's callback function using lambda. As in replace:

master.protocol("WM_DELETE_WINDOW", self.on_closing(master))

with:

master.protocol("WM_DELETE_WINDOW", lambda arg=master: self.onclosing(arg))

answered Mar 11, 2018 at 14:01

Nae

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2 Comments

Panos Over a year ago

Thanks for the answer! This is exactly what I needed.

Mike - SMT Over a year ago

master iteself is not some variable that will change over time so there is no reason to do arg=master. Simply master.protocol("WM_DELETE_WINDOW", lambda: self.on_closing(master)) will work fine here. On that note it is likely to be better to just do master.protocol("WM_DELETE_WINDOW", self.on_closing) and have the on_closing method do self.master.destroy().

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