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

     2 # By Michele Simoniato, inspired by brownian.py

     3 

     4 from Tkinter import *

     5 import random

     6 import sys

     7 

     8 WIDTH = 400

     9 HEIGHT = 300

    10 SIGMA = 10

    11 BUZZ = 2

    12 RADIUS = 2

    13 LAMBDA = 10

    14 FILL = 'red'

    15 

    16 stop = 0                                # Set when main loop exits

    17 root = None                             # main window

    18 

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

    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         try:

    28             canvas.move(p, dx, dy)

    29         except TclError:

    30             break

    31         else:

    32             yield None

    33 

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

    35     particle.next()

    36     dt = random.expovariate(LAMBDA)

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

    38 

    39 def main():

    40     global root, stop

    41     root = Tk()

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

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

    44     np = 30

    45     if sys.argv[1:]:

    46         np = int(sys.argv[1])

    47     for i in range(np):                  # start the dance

    48         move(particle(canvas))

    49     try:

    50         root.mainloop()

    51     finally:

    52         stop = 1

    53 

    54 if __name__ == '__main__':

    55     main()