Invalid command name while executing ("after" script)

Question

As solve this problem? I'm running this code, window is created, but in console appears message on the error. I think problem the fact that is "after" loop not terminate but the window already destroyed.

Code:

import Tkinter as tk
import time

class App():
    def __init__(self):
        self.root = tk.Tk()
        self.label = tk.Label(text="")
        self.label.pack()
        self.update_clock()
        self.root.mainloop()

    def update_clock(self):
        now = time.strftime("%H:%M:%S")
        self.label.configure(text=now)
        self.root.after(1000, self.update_clock)

app=App()

A message in console:

invalid command name "66120320callit"
while executing
"66120320callit"
("after" script)

Sorry for my small information in first post. I'm using Spyder IDE, and bugs see in spyder console, wherein run repeatedly my code. A description this bugs I find in the python bug tracker as "wait_variable hangs at exit"

Answer 1

If you destroy the window, whatever "after" jobs that have already been scheduled may run. If the window is destroyed and this job interacts with a widget that has been deleted, you'll get this error.

You can either put a try around the code and ignore such an error, check that the window exists before trying to configure it, or put a handler in for when the main window is destroyed to delete any pending "after" jobs.

Answer 2

Background

I was getting these 'errors' as well. They're not actual exceptions, they're just annoying to see being spammed in the terminal when running unittests.

I had tried a lot of things, including overriding the after method in tkinter.Tk to keep track of any queued methods and then calling tkinter.Tk.after_cancel() automatically before calling tkinter.Tk.destroy() as @GabrielStaples commented.

So I was getting these errors even though there were no queued after methods at the point of destroy() being called.

My solution

What worked for me was calling tkinter.Tk.quit() to destroy the window instead of destroy(). I read that quit() doesn't stop the mainloop but it seems fine. Any methods queued by after aren't called after quit() has been called.

Perhaps somebody could explain any consequences I'm not aware of if there are any