# 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()