How can I schedule updates (f/e, to update a clock) in tkinter?

Question

I'm writing a program with Python's tkinter library.

My major problem is that I don't know how to create a timer or a clock like hh:mm:ss.

I need it to update itself (that's what I don't know how to do); when I use time.sleep() in a loop the whole GUI freezes.

Answer 1

Tkinter root windows have a method called after which can be used to schedule a function to be called after a given period of time. If that function itself calls after you've set up an automatically recurring event.

Here is a working example:

# for python 3.x use 'tkinter' rather than 'Tkinter' 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() 

Bear in mind that after doesn't guarantee the function will run exactly on time. It only schedules the job to be run after a given amount of time. It the app is busy there may be a delay before it is called since Tkinter is single-threaded. The delay is typically measured in microseconds.