学习 Python，使用《 Python 编程：从⼊门到实践》，外星人入侵的主程序alien_invasion.py 运行后，只能出现一个空白窗口，而不能出现程序预设的飞机等其他任何东西。非常迷惑，恳请高人指点一下，感谢！感谢！主程序如下： import pygame from pygame.sprite import Group from settings import Settings from game_stats import GameStats from scoreboard import Scoreboard from button import Button from ship import Ship import game_functions as gf def run_game(): # Initialize pygame, settings, and screen object. pygame.init() ai_settings = Settings() screen = pygame.display.set_mode( (ai_settings.screen_width, ai_settings.screen_height)) pygame.display.set_caption("Alien Invasion") # Make the Play button. play_button = Button(ai_settings, screen, "Play") # Create an instance to store game statistics, and a scoreboard. stats = GameStats(ai_settings) sb = Scoreboard(ai_settings, screen, stats) # Set the background color. bg_color = (230, 230, 230) # Make a ship, a group of bullets, and a group of aliens. ship = Ship(ai_settings, screen) bullets = Group() aliens = Group() # Create the fleet of aliens. gf.create_fleet(ai_settings, screen, ship, aliens) # Start the main loop for the game. while True: gf.check_events(ai_settings, screen, stats, sb, play_button, ship, aliens, bullets) if stats.game_active: ship.update() gf.update_bullets(ai_settings, screen, stats, sb, ship, aliens, bullets) gf.update_aliens(ai_settings, screen, stats, sb, ship, aliens, bullets) gf.update_screen(ai_settings, screen, stats, sb, ship, aliens, bullets, play_button) run_game()