1# Brownian motion -- an example of a multi-threaded Tkinter program.
2
3from Tkinter import *
4import random
5import threading
6import time
7import sys
8
9WIDTH = 400
10HEIGHT = 300
11SIGMA = 10
12BUZZ = 2
13RADIUS = 2
14LAMBDA = 10
15FILL = 'red'
16
17stop = 0                                # Set when main loop exits
18
19def 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
34def 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
50main()
51