tkinter questions--- part 2

[ironsheep]

from tkinter import *
import random
import time
 
tk=Tk()
canvas=Canvas(tk, width=500, height=400)
canvas.pack()
 
class Ball:
    def__init__(self):
        self.shape = canvas.create_oval(10,10,60,60,fill="red")
        self.xspeed= 3
        self.yspeed= 4
 
    def move(self):
        canvas.move(self.shape, self.xspeed, self.yspeed)
        position= canvas.coords(ball)
        if position[3]>= 400 or position[1] <= 0:
            self.yspeed= -self.yspeed
        if position[2] >= 500 or position[0] <= 0:
            self.xspeed= -self.xspeed
         
ball1= Ball()
 
while True:
    ball1.move()
    tk.update()
    time.sleep(.01)
 

I do double underscore and I still get syntax error