Python 在 Pygame 中，图像在移动到游戏窗口的另一个位置时不会被删除

我一直在我的Mac电脑上试用Pygame游戏库，当我try 在游戏窗口周围移动一个图像时，由于某种原因，它不会被删除.

我试图运行的代码:

import pygame

pygame.init()

# Creates the screen.
screen = pygame.display.set_mode([800, 600])
pygame.display.set_caption("Space Invaders")
icon = pygame.image.load("ufo.png")
pygame.display.set_icon(icon)

# Player sprite.
playerImg = pygame.image.load("player.png")
playerX = 350
playerY = 500
playerX_change = 0

# Function to draw the player
def player(x, y):
  screen.blit(playerImg, (playerX, playerY))

# Game loop
running = True
while running:
  for event in pygame.event.get():
    if event.type == pygame.QUIT:
        running = False
    if event.type == pygame.KEYDOWN:
        if event.key == pygame.K_LEFT:
            playerX_change = -0.1
            print("Left key is pressed!")
        if event.key == pygame.K_RIGHT:
            playerX_change = 0.1
            print("Right key is pressed!")

    if event.type == pygame.KEYUP:
        if event.key == pygame.K_LEFT or event.key == pygame.K_RIGHT:
            playerX_change = 0

playerX += playerX_change

我曾try 在我的电脑上运行类似的代码，它的工作原理与预期一致.我不知道该怎么办.