【问题标题】：Python Crash Course, 2nd edition. Sideways shooter. Aliens keep moving down until the top row hits the bottomPython 速成课程，第 2 版。侧身射手。外星人继续向下移动，直到顶行撞到底部
【发布时间】：2023-04-03 09:48:01
【问题描述】：

您好，我正在努力让我的横向射击游戏加快速度。但是当我试图将外星人舰队向下和向左移动时遇到了问题。我已经设置了self.rect.bottom >= screen_rect.bottom。但这段代码只对我的第一排外星人有反应。我尝试设置一个数值，但这并没有给我想要的结果。非常感谢任何帮助。

这是我的外星人代码：

外星人.py

def check_edges(self):
    """Return True if alien is at edge of screen."""
    screen_rect = self.screen.get_rect()
    if self.rect.bottom >= screen_rect.bottom or self.rect.top <= 0:
        return True

def update(self):
    """Move the alien up or down."""
    self.y += (self.settings.alien_speed *
                    self.settings.fleet_direction)

    self.rect.y = self.y

在 alien_invasion.py 中

def _update_aliens(self):
    """
    Check if the fleet is at an edge,
      then update the positions of all aliens in the fleet.
    """
    self._check_fleet_edges()
    self.aliens.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 height.
    alien = Alien(self)
    alien_width = alien.rect.width
    
    alien_height = alien.rect.height
    
    # Determine the number of  rows of aliens that fit on the screen.
    ship_width = self.ship.rect.width 
    available_space_x = (self.settings.screen_width - 
        (2 * alien_width) + ship_width)
    number_rows = available_space_x // (3 * alien_width)

    
    available_space_y = self.settings.screen_height + (2 * alien_height)
    number_aliens_y = available_space_y // (2 * alien_height)

    # Create full fleet of aliens.
    for alien_number in range(number_aliens_y):
        for row_number in range(number_rows):
            self._create_alien(alien_number, row_number)
        
def _create_alien(self, alien_number, row_number):
    """Create an alien and place it in the row."""
    alien = Alien(self)
    alien_width = alien.rect.width
    alien_height = alien.rect.height

    alien.rect.x = 1200 - (2 * alien_width) - (2 * alien.rect.width) * row_number
    
    alien.y = alien_height + 2 * alien_height * alien_number
    alien.rect.y = alien.y
    self.aliens.add(alien)

def _check_fleet_edges(self):
    """Respond appropriately if any aliens have reached an edge."""
    for alien in self.aliens.sprites():
        if alien.check_edges():
            self._change_fleet_direction()
            break

def _change_fleet_direction(self):
    """Drop the entire fleet and change the fleet's direction"""
    for alien in self.aliens.sprites():
        alien.rect.x -= self.settings.fleet_left_speed
    self.settings.fleet_direction *= -1

【问题讨论】：

    标签：
    python
    loops
    pygame