上传文件至 ''

alien.py

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+import pygame
+from pygame.sprite import Sprite
+
+class Alien(Sprite):
+    """表示单个外星人的类"""
+
+    def __init__(self, ai_settings, screen):
+        """初始化外星人并设置其初始位置"""
+        super().__init__()
+        self.screen = screen
+        self.ai_settings = ai_settings
+
+        # 加载外星人图像，并设置其rect属性
+        self.image = pygame.image.load('images/alien.bmp')
+        self.rect = self.image.get_rect()
+
+        # 每个外星人初始都在屏幕左上角，设置为其宽高以进行留白
+        self.rect.x = self.rect.width
+        self.rect.y = self.rect.height * 2
+
+        self.x = float(self.rect.x)
+
+
+    def update(self):
+        """向左或向右右移动外星人"""
+        self.x += self.ai_settings.alien_speed_factor * self.ai_settings.fleet_direction
+        self.rect.x = self.x
+
+
+    def check_edges(self):
+        screen_rect = self.screen.get_rect()
+        if self.rect.right >= screen_rect.right:
+            return True
+        elif self.rect.left <= screen_rect.left:
+            return True