# Brownian motion -- an example of a NON multi-threaded Tkinter program ;)

# By Michele Simoniato, inspired by brownian.py

from Tkinter import *

import random

import sys

WIDTH = 400

HEIGHT = 300

SIGMA = 10

BUZZ = 2

RADIUS = 2

LAMBDA = 10

FILL = 'red'

stop = 0                                # Set when main loop exits

root = None                             # main window

def particle(canvas):                   # particle = iterator over the moves

    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)

        try:

            canvas.move(p, dx, dy)

        except TclError:

            break

        else:

            yield None

def move(particle): # move the particle at random time

    particle.next()

    dt = random.expovariate(LAMBDA)

    root.after(int(dt*1000), move, particle)

def main():

    global root, 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):                  # start the dance

        move(particle(canvas))

    try:

        root.mainloop()

    finally:

        stop = 1

if __name__ == '__main__':

    main()