# Brownian motion -- an example of a multi-threaded Tkinter program.

from Tkinter import *

import random

import threading

import time

import sys

WIDTH = 400

HEIGHT = 300

SIGMA = 10

BUZZ = 2

RADIUS = 2

LAMBDA = 10

FILL = 'red'

stop = 0                                # Set when main loop exits

def particle(canvas):

    r = RADIUS

    x = random.gauss(WIDTH/2.0, SIGMA)

    y = random.gauss(HEIGHT/2.0, SIGMA)

    p = canvas.create_oval(x-r, y-r, x+r, y+r, fill=FILL)

    while not stop:

        dx = random.gauss(0, BUZZ)

        dy = random.gauss(0, BUZZ)

        dt = random.expovariate(LAMBDA)

        try:

            canvas.move(p, dx, dy)

        except TclError:

            break

        time.sleep(dt)

def main():

    global stop

    root = Tk()

    canvas = Canvas(root, width=WIDTH, height=HEIGHT)

    canvas.pack(fill='both', expand=1)

    np = 30

    if sys.argv[1:]:

        np = int(sys.argv[1])

    for i in range(np):

        t = threading.Thread(target=particle, args=(canvas,))

        t.start()

    try:

        root.mainloop()

    finally:

        stop = 1

main()