Pygame精灵上的恒定动画

我最近一直在尝试制作一个动画,其中我的精灵在2张图片之间不停地来回移动。我想知道该怎么做。如果能提供任何帮助,我将不胜感激

import pygame
import os
import time
import sys

image1 = pygame.image.load("image1.png")
image2 = pygame.image.load("image2.png")

class sprite(object): 
    def __init__(self):
        super(sprite, self).__init__()
        self.x = 0
        self.y = 0

    def handle_keys(self):

        key = pygame.key.get_pressed()
        distance = 1 
        if key[pygame.K_DOWN]: 
            self.y += distance

        if key[pygame.K_UP]:
            self.y -= distance

        if key[pygame.K_RIGHT]: 
            self.x += distance
        if key[pygame.K_LEFT]: 
            self.x -= distance


    def draw(self, surface):

        surface.blit(self.image, (self.x, self.y))


pygame.init()
screen = pygame.display.set_mode((1600, 800))

sprite=sprite() 
clock = pygame.time.Clock()

running = True
while running:

    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
            running = False

    sprite.handle_keys() 

    screen.fill((255,255,255)) 
    sprite.draw(screen) 
    pygame.display.update() 

    clock.tick(40)