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      1 # Brownian motion -- an example of a multi-threaded Tkinter program.
      2 
      3 from Tkinter import *
      4 import random
      5 import threading
      6 import time
      7 import sys
      8 
      9 WIDTH = 400
     10 HEIGHT = 300
     11 SIGMA = 10
     12 BUZZ = 2
     13 RADIUS = 2
     14 LAMBDA = 10
     15 FILL = 'red'
     16 
     17 stop = 0                                # Set when main loop exits
     18 
     19 def particle(canvas):
     20     r = RADIUS
     21     x = random.gauss(WIDTH/2.0, SIGMA)
     22     y = random.gauss(HEIGHT/2.0, SIGMA)
     23     p = canvas.create_oval(x-r, y-r, x+r, y+r, fill=FILL)
     24     while not stop:
     25         dx = random.gauss(0, BUZZ)
     26         dy = random.gauss(0, BUZZ)
     27         dt = random.expovariate(LAMBDA)
     28         try:
     29             canvas.move(p, dx, dy)
     30         except TclError:
     31             break
     32         time.sleep(dt)
     33 
     34 def main():
     35     global stop
     36     root = Tk()
     37     canvas = Canvas(root, width=WIDTH, height=HEIGHT)
     38     canvas.pack(fill='both', expand=1)
     39     np = 30
     40     if sys.argv[1:]:
     41         np = int(sys.argv[1])
     42     for i in range(np):
     43         t = threading.Thread(target=particle, args=(canvas,))
     44         t.start()
     45     try:
     46         root.mainloop()
     47     finally:
     48         stop = 1
     49 
     50 main()
     51