python新手提问 谢谢大神了

from tkinter import*
import random
import time

class Ball:
def __init__(self, canvas, color):
self.canvas = canvas
self.id = canvas.create_oval(10, 10, 25, 25, fill=color)
self.canvas.move(self.id, 245, 100)
starts = [-3, -2, -1, 1, 2, 3]
random.shuffle(starts)
self.x = starts[0]
self.y = -3
self.canvas_height = self.canvas.winfo_height
self.canvas_width = self.canvas.winfo_width

def draw(self):
self.canvas.move(self.id, self.x, self.y)
pos = self.canvas.coords(self.id)
if pos(1) <= 0:
self.y = 3
if pos(3) >= self.canvas_height:
self.y = -3
if pos(0) <= 0:
self.x = 3
if pos(2) >= self.canvas_width:
self.x = -3
tk = Tk()
tk.title("Game")
tk.resizable(0, 0)
tk.wm_attributes("-topmost", 1)
canvas = Canvas(tk, width=500, height=400, bd=0, highlightthickness=0)
canvas.pack()
tk.update()

ball = Ball(canvas, 'red')

while 1:
ball.draw()
tk.update_idletasks()
tk.update()
time.sleep(0.01)

错误如下
C:\Users\admin\AppData\Local\Programs\Python\Python35\python.exe C:/Users/admin/PycharmProjects/untitled3/ball.py
Traceback (most recent call last):
File "C:/Users/admin/PycharmProjects/untitled3/ball.py", line 42, in
ball.draw()
AttributeError: 'Ball' object has no attribute 'draw'

Process finished with exit code 1

这个报错的原因是你的缩进少了，导致 draw() 方法不在 Ball类 里面， 办法是从17到27行全部再往后缩进一个单位。不幸的是，我刚调试了一下，你这段代码不光是有这一个问题。靠你自己慢慢找了。

当方法以__开头后,会认为它是一个私有的方法，外部不能调用，其实是因为python帮我们改名了，如上所式的___haha方法变成了 _+类名+原方法名的形式 属性也是一样