Python GUI Programming with Tkinter

Using queues to communicate between threads

Before editing our application code, let's create a simpler example application to make sure we understand how to use Queue to communicate between threads.

Start with a long-running thread:

from threading import Thread
from time import sleep

class Backend(Thread):

    def __init__(self, queue, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.queue = queue

    def run(self):
        self.queue.put('ready')
        for n in range(1, 5):
            self.queue.put(f'stage {n}')
            print(f'stage {n}')
            sleep(2)
        self.queue.put('done')

The Backend object is a subclass of Thread that takes a Queue object as an argument and saves it as an instance property. Its run method simulates a long-running four-phase process using print() and ...