pygame向左和向右移动问题

import pygame
from pygame.locals import *

pygame.init()
window = pygame.display.set_mode((width, height))

x = initial_x  # 游戏对象的初始横坐标
y = initial_y  # 游戏对象的初始纵坐标
speed = 5     # 游戏对象的移动速度

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

    keys = pygame.key.get_pressed()
    if keys[K_LEFT]:
        x -= speed
    if keys[K_RIGHT]:
        x += speed

    # 清屏
    window.fill((0, 0, 0))
    # 绘制游戏对象
    pygame.draw.rect(window, (255, 255, 255), (x, y, object_width, object_height))
    # 刷新屏幕
    pygame.display.update()

pygame.quit()