python 《从入门到实践》外新人大战报错，是怎么回事？

Question

代码如下：

import sys
from time import sleep

import pygame


from settings import settings

from game_stats import GameStats

from ship import ship

from bullet import Bullet

from alien import Alien



class alieninvasion:
    
    def __init__(self):
        pygame.init()
        self.settings = settings()


        self.screen = pygame.display.set_mode((self.settings.screen_width, self.settings.screen_height))

        self.screen = pygame.display.set_mode((1200,800))
        pygame.display.set_caption("weijia.game")

        self.stats = GameStats(self)
        self.bg_color = (0,0,139)
        self.ship = ship(self)
        self.bullets = pygame.sprite.Group()
        self.aliens = pygame.sprite.Group()
        
        self._create_fleet()


    
        



    def _create_fleet(self):
        alien = Alien(self)
        alien_width, alien_height = alien.rect.size
        available_space_x = self.settings.screen_width - (2 * alien_width)
        number_aliens_x = available_space_x // (2 * alien_width)

        ship_height = self.ship.rect.height
        available_space_y = (self.settings.screen_height -(3 * alien_height) - ship_height)
        number_rows = available_space_y // (2 * alien_height)



        for row_number in range(number_rows):
            for alien_number in range(number_aliens_x):
                self._create_alien(alien_number, row_number)
                
    def _create_alien(self, alien_number, row_number):
        alien = Alien(self)
        alien_width, alien_height = alien.rect.size
        alien_width = alien.rect.width
        alien.x = alien_width + 2 * alien_width * alien_number
        alien.rect.x = alien.x
        alien.rect.y = alien.rect.height + 2 * alien.rect.height * row_number
        self.aliens.add(alien)


    def _check_fleet_edges(self):
        for alien in self.aliens.sprites():
            if alien.check_edges():
                self._change_fleet_direction()
                break




    def _change_fleet_direction(self):

        for alien in self.aliens.sprites():
            alien.rect.y += self.settings.fleet_drop_speed
        self.settings.fleet_direction *= -1



    def _check_aliens_bottom(self):

        screen_rect = self.screen.get_rect()
        for alien in self.aliens.sprites():
            if alien.rect.bottom >= screen_rect.bottom:

                self._ship_hit()
                break


    
    


    def _update_aliens(self):
        self._check_fleet_edges()
        self.aliens.update()


        if pygame.sprite.spritecollideany(self.ship, self.aliens):
            self._ship_hit()


        self._check_aliens_bottom()



    def run_game(self):
        while True:
            self.check_events()
            if self.stats.game_active:
                self.ship.update()
                self._update_bullets()
                self._update_aliens()

            
            self._update_screen()
            
            

    def check_events(self, *event):
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                sys.exit()
            elif event.type == pygame.KEYDOWN: 
                if event.key == pygame.K_RIGHT:#key 
                    self.ship.moving_right = True 
                elif event.key == pygame.K_LEFT: #key
                    self.ship.moving_left = True 
                elif event.key == pygame.K_UP:#key
                    self._fire_bullet()
                elif event.key == pygame.K_q:
                    sys.exit()
            elif event.type == pygame.KEYUP: 
                if event.key == pygame.K_LEFT: #key
                    self.ship.moving_left = False
                elif event.key == pygame.K_RIGHT:#key 
                    self.ship.moving_right = False
             
            
            
            


                
            
    def _fire_bullet(self):
        if len(self.bullets) < self.settings.bullets_allowed:
            new_bullet = Bullet(self)
            self.bullets.add(new_bullet)
    

    def _update_bullets(self):
        self.bullets.update()
        for bullet in self.bullets.copy():
            if bullet.rect.bottom <= 0:
                self.bullets.remove(bullet)
        self._check_bullet_alien_collisions()




    def _check_bullet_alien_collisions(self):

        collisions = pygame.sprite.groupcollide(self.bullets, self.aliens, True, True)
        if not self.aliens:
            self.bullets.empty()
            self._create_fleet()
    



    def _update_screen(self): 
        self.screen.fill(self.bg_color) 
        self.screen.fill(self.settings.bg_color) 
        self.ship.blitme()
        for bullet in self.bullets.sprites():
            bullet.draw_bullet()

        self.aliens.draw(self.screen)

        pygame.display.flip()


    
            
    def _ship_hit(self):


        if self.stats.ships_left > 0:
            self.stats.ships_left -= 1


            self.aliens.empty()
            self.bullets.empty()

            self._create_fleet()
            self.ship.center_ship()

            sleep(0.5)

        else:
            self.stats.game_active = False


        


if __name__ == '__main__':
    ai = alieninvasion()
    ai.run_game()
    

但是当外星人撞到飞船就会报错，报错代码如下：
pygame 2.1.2 (SDL 2.0.18, Python 3.7.2)
Hello from the pygame community. https://www.pygame.org/contribute.html
Traceback (most recent call last):
  File "C:\Users\Administrator\Desktop\新建文件夹\main.py", line 218, in <module>
    ai.run_game()
  File "C:\Users\Administrator\Desktop\新建文件夹\main.py", line 121, in run_game
    self._update_aliens()
  File "C:\Users\Administrator\Desktop\新建文件夹\main.py", line 108, in _update_aliens
    self._ship_hit()
  File "C:\Users\Administrator\Desktop\新建文件夹\main.py", line 197, in _ship_hit
    if self.stats.ships_left > 0:
AttributeError: 'GameStats' object has no attribute 'ships_left'

Answer 1

检查GameStats这个类里面有没有ships_left，或者写错了