[Python-Dev] threadless brownian.py (original) (raw)

Michele Simionato michele.simionato at gmail.com
Sun Apr 9 18:39:11 CEST 2006

Recently I downloaded Python 2.5a1 and I have started playing with it. In doing so, I have been looking at the Demo directory in the distribution, to check if demos of the new features have been added there. So, I rediscovered brownian.py, in Demo/tkinter/guido. I just love this little program, because it reminds myself of one my first programs, a long long time ago (a brownian motion in AmigaBasic, with sprites!). It is also one of the first programs I looked at, when I started studying threads four years ago and I thought it was perfect. However, nowadays I know better and I have realized that brownian.py is perfect textbook example of a case where you don't really need threads, and you can use generators instead. So I thought it would be nice to add a threadless version of brownian.py in the Demo directory. Here it is. If you like it, I donate the code to the PSF!

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

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()

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