Tkinter canvas flickering
<p>I'm attempting to implement a simple Pong game in Python using Tkinter, but unfortunately I'm having some major issues with flickering. I'm using a Canvas widget that covers the entire window and I'm drawing rectangles on said canvas many times per second. When I do this all drawn rectangles flicker regularly while the game is running, disappearing for a fraction of a second before appearing again.</p>

<p>A simple example of the logic I use for drawing in my game can be seen below, by running it you should be able to see the flickering in action:</p>

<pre><code>from tkinter import *
import threading, time

def loop():
    FRAME_TIME = 1 / 60
    while True:
        render()
        time.sleep(FRAME_TIME)

def render():
    canvas.delete(ALL)
    canvas.create_rectangle(0, 0, WIDTH, HEIGHT, fill='black')

WIDTH = 800
HEIGHT = 600

root = Tk()
canvas = Canvas(root, width=800, height=600)
canvas.pack()
threading.Thread(target=loop, daemon=True).start()
root.mainloop()
</code></pre>

<p>Any ideas as to what is causing it?</p>