# Tk_fizzle.py

# Tk_fizzle.py

import Tkinter as tk
import random

def create_bubbles(canvas):
    bubbles = []
    for __ in range(30):
        x = random.randint(0, 400)
        y = random.randint(0, 400)
        r = random.randint(5, 30)
        bubble = canvas.create_oval(x-r, y-r, x+r, y+r)
        bubbles.append( [bubble, r] )
    return bubbles


def moves_bubbles(canvas, bubbles):
    for bubble, r in bubbles:
        x1, y1, x2, y2 = canvas.coords(bubble)
        sz = 15-int(r/2)
        y1 -= 1+sz
        y2 -= 1+sz
        if y2 <= 0:
            y1 = 300
            y2 = y1 + 2*r

        # set position
        canvas.coords(bubble, x1, y1, x2, y2)

    root.after(40, moves_bubbles, canvas, bubbles)

# --- main ---

root = tk.Tk()

canvas = tk.Canvas(root)
canvas.pack()

bubbles = create_bubbles(canvas)

# run after 40ms - it gives 25FPS
root.after(40, moves_bubbles, canvas, bubbles)

root.mainloop()