balls.py

from Tkinter import *
import random

def animation_threshold():
  global i
  if i == 50000:
    i = 0
    return False
  else:
    i += 1
    return True

def change_dir(item):
  global objects
  objects[item][0] *= -1
  cv.move(objects[item][1], objects[item][0], 0)
  cv.update()

def update_objects():
  global objects
  for i in range(0, len(objects)):
    x = cv.coords(objects[i][1])[0]
    if x < 5:
      change_dir(i)
    elif x > 470:
      change_dir(i)
    else:
      cv.move(objects[i][1], objects[i][0], 0)
      cv.update()

def add_object(event = None):
  global objects
  x, y = random.randint(0, 475), random.randint(25, 475)
  objects.append([5, cv.create_oval(x, y, x + 25, y + 25, fill = "blue")])
  cv.update()

root = Tk()
w = 500
h = 500
cv = Canvas(width = w, height = h)
cv.pack()
cv.update()

objects = []
i = 0
root.bind("a", add_object)
add_object()
while True:
  if animation_threshold(): continue
  update_objects()

root.mainloop()