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我正在 Eric Matthes 的“Python Crash Course”一书中学习基本的 Python，现在我正在学习从书中创建一个 2D 游戏项目。

我在第 13 章尝试创建外星舰队的第一排时遇到了一个问题。问题是没有其他外星飞船，而代码函数应该创建一个包含许多外星飞船的单行。这是alien_invasion.py的详细信息

import sys

import pygame

from settings import Settings

from ship import Ship 

from bullet import Bullet

from alien import Alien

from pygame.locals import *

class AlienInvasion:
    """Overall class to manage game assets and behavior."""

    def __init__(self):
        """Initialize the game, and create game resources."""
        pygame.init()

        self.settings = Settings()

        

        # Set the background color.
        self.screen = pygame.display.set_mode((0, 0), pygame.FULLSCREEN)
        self.settings.screen_width = self.screen.get_rect().width
        self.settings.screen_height = self.screen.get_rect().height
        pygame.display.set_caption("Alien Invasion")

        self.ship = Ship(self)
        self.bullets = pygame.sprite.Group()
        self.aliens = pygame.sprite.Group()

        self._create_fleet()


    def run_game(self):
        """Start the main loop for the game."""
        while True:
            self._check_events()
            self.ship.update()

            # Get rid of bullets that have disappeared.
            for bullet in self.bullets.copy():
                if bullet.rect.bottom <= 0:
                    self.bullets.remove(bullet)

            self._update_bullets()
            self._update_screen()   
    

            # Redraw the screen during each pass through the loop..
            self.screen.fill(self.settings.bg_color)
            

    def _check_events(self):
        """Respond to keypresses and mouse events."""
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                sys.exit()

            elif event.type == pygame.KEYDOWN:
                self._check_keydown_events(event)
            elif event.type == pygame.KEYUP:
                self._check_keyup_events(event)


    def _check_keydown_events(self, event):
        """Respond to keypresses."""
        if event.key == pygame.K_RIGHT:
            self.ship.moving_right = True
        elif event.key == pygame.K_LEFT:
            self.ship.moving_left = True

        elif event.key == pygame.K_q:
            sys.exit()
        elif event.key == pygame.K_SPACE:
            self._fire_bullet()

    def _check_keyup_events(self, event):
        """Respond to key releases."""
        if event.key == pygame.K_RIGHT:
            self.ship.moving_right = False
        elif event.key == pygame.K_LEFT:
            self.ship.moving_left = False
        

    def _fire_bullet(self):
        """Create a new bullet and add it to the bullets group."""
        if len(self.bullets) < self.settings.bullets_allowed:
            new_bullet = Bullet(self)
            self.bullets.add(new_bullet)    

    def _update_bullets(self):
        """Update position of bullets and get rid of old bullets."""
        # Update bullet positions.
        self.bullets.update()


    def _create_fleet(self):
        """Create the fleet of aliens."""
        # Create an alien and find the number of aliens in a row.
        # Spacing between each alien is equal to one alien width.
        alien = Alien(self)
        alien_width = alien.rect.width
        available_space_x = self.settings.screen_width - (2 * alien_width)
        number_aliens_x = available_space_x // (2 * alien_width)


        # Create the first row of aliens.
        for alien_number in range(number_aliens_x):
            # Create an alien and place it in the row.
            alien = Alien(self)
            alien.x = alien_width + 2 * alien_width * alien_number
            alien.rect_x = alien.x
            self.aliens.add(alien)


    def _update_screen(self):
        """Updates images on the screen, and flip to the new screen."""
        self.screen.fill(self.settings.bg_color)
        self.ship.blitme()
        for bullet in self.bullets.sprites():
            bullet.draw_bullet() 

        self.aliens.draw(self.screen)

        # Make the most recently drawn screen visible.
        pygame.display.flip()

if __name__ == '__main__':
    # Make a game instance, and run the game.
    ai = AlienInvasion()
    ai.run_game()

这是外星人.py

import pygame
from pygame.sprite import Sprite

class Alien(Sprite):
    """ A class tp represent a single alien in te fleet. """

    def __init__(self, ai_game):
        """Initilize the alien and set its starting position."""
        super().__init__()
        self.screen = ai_game.screen

        # Load the alien image and set its rect attribute.
        self.image = pygame.image.load('images/alien-ship.png')
        self.image = pygame.transform.scale(self.image, (70,70))
        self.rect = self.image.get_rect()

        # Start each new alien near the top left of the screen.
        self.rect.x = self.rect.width
        self.rect.y = self.rect.height

        # Store the alien's exact horizontal position.
        self.x = float(self.rect.x)

还有一件事，我没有使用书中提供的图像文件，而是使用了自己的文件，其中文件扩展名是 png 而不是 bmp。

这是我第二次在这个平台发问题，所以可能有些地方发错了，我提前道歉。

谢谢您的帮助。

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