# Brownian motion -- an example of a multi-threaded Tkinter program.
from tkinter import *
import random
import threading
import time
import sys
#画布大小
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)
 #粒子数目
 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()