各位大佬，帮我看下move（）错在哪里，pygame运行报错
import pygame,sys
pygame.init()
screen = pygame.display.set_mode([640,640])
background = pygame.Surface(screen.get_size())
background.fill([255,255,255])
clock = pygame.time.Clock()
class Ball(pygame.sprite.Sprite):
def __init__(self,image_file, speed,location):
pygame.sprite.Sprite.__init__(self)
self.image = pygame.image.load(image_file)
self.rect = self.image.get_rect()
self.rect.left,self.rect.top = location
self.speed = speed
def move(self):
if self.rect.left <=screen.get_rect().left or \
self.rect.right >= screen.get_rect().right:
self.speed[0] = - self.speed[0]
newpos = self.rect.move(self.speed)
self.rect = newpos
my_ball = Ball("beach-ball-free-png-210x210.png",[10,0],[20,20])
running = True
while running:
for event in pygame.event.get():
if event.type == pygame.QUIT:
running = False
clock.tick(30)
screen.blit(background,(0,0))
my_ball.move()
screen.blit(my_ball.image,my_ball.rect)
pygame.display.flip()
pygame.quit()