Question

I’m just getting started with Tk and using it in python. I set up a button that does a ton (like two minutes worth) of stuff behind the scenes when you press it. I also set up a status text to show what’s going on while this is happening. I set it up like this:

status_text = Tkinter.StringVar()
ttk.Button(mainframe, text="Stats!", command=go).grid(column=1, row=4)

def go(*args):
    status_text.set("Logging in...")
    do_lots_of_stuff()
    status_text.set("Doing stuff #1...")
    do_even_more_stuff()
    status_text.set("Success!")

The problem is that when you press that button the window freezes, and the status text never actually changes. It looks broken, and doesn’t come out of this state until all the processing finishes 2-3 minutes later. How do I make it not freeze and update the status text?

Answer 1

It’s time to learn multithreading!

What’s happening is that the GUI (main thread) is waiting for the method to return so that it can continue updating the interface.

You’ll want to cause the action of a button to spawn a threading.Thread instead of running the heavy code in the main thread. You’ll also want to create a Queue to access the data from the other thread (since sending GUI requests should ONLY be made from the main thread).

import threading, Queue #queue in 3.x

my_queue = Queue.Queue()

def go(*args):
    my_thread = threading.Thread(target=function_that_does_stuff)

def function_that_does_stuff():
    my_queue.put("Logging in...")
    do_lots_of_stuff()
    my_queue.put("Doing stuff #1...")
    do_even_more_stuff()
    my_queue.put("Success!")

Then you’ll need a function that is run when the update event happens.

def OnUpdate(*args):
    try:
        status_text.set(my_queue.get())
    except Queue.Empty:
        pass