title: Tkinter canvas flickering
body: <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>