Making a countdown timer with Python and Tkinter?

Question

I want to set a label in Tkinter using my countdown timer function. Right now all it does is set the lable to "10" once 10 is reached and I don't really understand why. Also, even if I have the timer print to a terminal instead the "Time's up!" bit never prints.

import time
import tkinter as tk

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

    # Define a timer.
    def countdown(self):
        p = 10.00
        t = time.time()
        n = 0
        # Loop while the number of seconds is less than the integer defined in "p"
        while n - t < p: 
            n = time.time()
            if n == t + p:
                self.label.configure(text="Time's up!")
            else:
                self.label.configure(text=round(n - t))

app=App()

here's a code example of a countdown implemented using Tkinter — jfs
– jfs, Commented Mar 3, 2015 at 9:15

Bryan Oakley · Accepted Answer · 2012-05-15 11:12:52Z

14

Tkinter already has an infinite loop running (the event loop), and a way to schedule things to run after a period of time has elapsed (using after). You can take advantage of this by writing a function that calls itself once a second to update the display. You can use a class variable to keep track of the remaining time.

import Tkinter as tk

class ExampleApp(tk.Tk):
    def __init__(self):
        tk.Tk.__init__(self)
        self.label = tk.Label(self, text="", width=10)
        self.label.pack()
        self.remaining = 0
        self.countdown(10)

    def countdown(self, remaining = None):
        if remaining is not None:
            self.remaining = remaining

        if self.remaining <= 0:
            self.label.configure(text="time's up!")
        else:
            self.label.configure(text="%d" % self.remaining)
            self.remaining = self.remaining - 1
            self.after(1000, self.countdown)

if __name__ == "__main__":
    app = ExampleApp()
    app.mainloop()

edited May 15, 2012 at 11:12

answered May 15, 2012 at 11:07

Bryan Oakley

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2 Comments

Ryan Hasse Over a year ago

That explains a lot, thank you. I was wondering why it only updates once the last item is reached even after I rewrote it a few different ways.

Bryan Oakley Over a year ago

@RyanHasse: the display only updates when Tkinter can respond to events that tell it to update the display. These events only get processed by the event loop. If you have your own loop, it will starve the event loop, preventing redraw requests from happening.

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