CODEWITHSUNDEEP
pythonooptkinter
Nate
Nate

Reputation: 105

Inconsistent Tkinter behavior at runtime after code changes

Note: I am not a programmer by trade or education, so bear with me. Take the following simple application: 

import tkinter as tk
root = tk.Tk()

class app(tk.Frame):
    def __init__(self, master=None):
        super().__init__(master)
        self.pack()
        self.create_widgets()

    def create_widgets(self):
        self.button1= tk.Button(self, text='1')
        self.button1.pack(side='top')

        self.quit_button= tk.Button(self, text='quit', command=self.quit_button.destroy())
        self.quit_button.pack(side='bottom')

application = app(root)
application.mainloop()

When I run this code, I am told destroy() isn't an method of quit_button. If I change it to:

self.quit_button= tk.Button(self, text='quit', command=self.dest)

and I add the method:

def dest(self):
    self.quit_button.destroy()

then it works - I assume this has something to do with the button being unable to reference itself while it's being created (please correct/enlighten me on this if you can since I don't fully understand this behavior).

However, what I'm really asking about is that the first time the program is run after I get this error, I get one window with both buttons, and X extra windows with only button1 (packed appropriately) where X is the number of times I incurred the error. Obviously I can just "not do that" but it would be extremely educative for me to understand how tkinter could be behaving this way. Is anyone here familiar enough with OOP to help? I create the root window before anything else, so there should be only one in any case.

Upvotes: 0

Views: 140

Answers (1)

martineau
martineau

Reputation: 123501

You've got a couple of problems in your code. All in the line:

self.quit_button= tk.Button(self, text='quit', command=self.quit_button.destroy())

The first is you're trying to reference self.quit_button at the same time you're creating it. The second, somewhat related issue, is the command=self.quit_button.destroy() part actually tries to call one of this non-existent Button's methods rather than just supplying a reference to it (because of the ()s following its name).

Here's a version with those problems fixed:

import tkinter as tk
root = tk.Tk()

class app(tk.Frame):
    def __init__(self, master=None):
        super().__init__(master)
        self.pack()
        self.create_widgets()

    def create_widgets(self):
        self.button1= tk.Button(self, text='1')
        self.button1.pack(side='top')

        self.quit_button = tk.Button(self, text='quit')
        self.quit_button.config(command=self.quit_button.destroy)  # set function to execute
        self.quit_button.pack(side='bottom')

application = app(root)
application.mainloop()

Upvotes: 1

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