《外星人入侵》AttributeError求助：Scoreboard对象无level_image属性

编写《外星人入侵》游戏时遇到AttributeError，提示'Scoreboard'对象没有'level_image'属性，对照《Python Crash Course》代码修改后仍未解决，怀疑prep_high_score调用存在问题。

报错栈信息 #

Traceback (most recent call last):
  File "c:\Users\hlehm\Onedrive Transfer\Python\Projects\Alien_Invasion\alien_invasion.py", line 272, in <module>
    ai.run_game()
  File "c:\Users\hlehm\Onedrive Transfer\Python\Projects\Alien_Invasion\alien_invasion.py", line 50, in run_game
    self._update_screen()
  File "c:\Users\hlehm\Onedrive Transfer\Python\Projects\Alien_Invasion\alien_invasion.py", line 258, in _update_screen
    self.sb.show_score()
  File "c:\Users\hlehm\Onedrive Transfer\Python\Projects\Alien_Invasion\scoreboard.py", line 75, in show_score
    self.screen.blit(self.level_image, self.level_rect)
AttributeError: 'Scoreboard' object has no attribute 'level_image'

原始Scoreboard类代码 #

import pygame.font

class Scoreboard:
    """A class to report scoring information"""


def __init__(self, ai_game):
    """Initialize scorekeeping attributes"""
    self.screen = ai_game.screen
    self.screen_rect = self.screen.get_rect()
    self.settings = ai_game.settings
    self.stats = ai_game.stats

    #Font settings for scoring information
    self.text_color = (30, 30, 30)
    self.font = pygame.font.SysFont(None, 48)

    #Prepare the initial score images
    self.prep_score()
    self.prep_high_score()


def prep_score(self):
    """Turn the score into a render image"""
    rounded_score = round(self.stats.score, -1)
    score_str = "{:,}".format(rounded_score)
    self.score_image = self.font.render(score_str, True, self.text_color, self.settings.bg_color)

    #Display the score at the top right of the screen
    self.score_rect = self.score_image.get_rect()
    self.score_rect.right = self.screen_rect.right - 20
    self.score_rect.top = 20


def prep_high_score(self):
    """Turn the high score into a rendered image"""
    high_score = round(self.stats.high_score, -1)
    high_score_str = "{:,}".format(high_score)
    self.high_score_image = self.font.render(
        high_score_str, True, self.text_color, self.settings.bg_color)


    #Center the high score at the top of the screen
    self.high_score_rect = self.high_score_image.get_rect()
    self.high_score_rect.centerx = self.screen_rect.centerx
    self.high_score_rect.top = self.screen_rect.top
    


def check_high_score(self):
    """Check to see if there's a new high score"""
    if self.stats.score > self.stats.high_score:
        self.stats.high_score = self.stats.score
        self.prep_high_score()
        self.prep_level()


def prep_level(self):
    """Turn the level into a rendered image"""
    level_str = str(self.stats.level)
    self.level_image = self.font.render(
        level_str, True, self.text_color, self.settings.bg_color)

    #Posistion the level below the score
    self.level_rect = self.level_image.get_rect()
    self.level_rect.right = self.score_rect.right
    self.level_rect.top = self.score_rect.bottom + 10


def show_score(self):
    """Draw scores and level to the screen"""
    self.screen.blit(self.score_image, self.score_rect)
    self.screen.blit(self.high_score_image, self.high_score_rect)
    self.screen.blit(self.level_image, self.level_rect)

问题根源与修复方案 #

核心问题1：类方法缩进错误 #

所有类方法（__init__、prep_score等）都未缩进至Scoreboard类的范围内，导致这些方法是全局函数而非类的成员方法。因此Scoreboard实例无法访问这些方法，自然不会执行prep_level创建level_image属性。

核心问题2：初始化时未调用prep_level #

即使修复缩进，原始__init__方法仅调用了prep_score和prep_high_score，未调用prep_level，游戏启动后第一次执行show_score时，level_image尚未被创建，依然会报错。

修复后的完整代码 #

import pygame.font

class Scoreboard:
    """用于显示得分信息的类"""

    def __init__(self, ai_game):
        """初始化得分统计属性"""
        self.screen = ai_game.screen
        self.screen_rect = self.screen.get_rect()
        self.settings = ai_game.settings
        self.stats = ai_game.stats

        # 得分信息的字体设置
        self.text_color = (30, 30, 30)
        self.font = pygame.font.SysFont(None, 48)

        # 准备初始的得分图像
        self.prep_score()
        self.prep_high_score()
        self.prep_level()  # 添加该行，初始化等级图像

    def prep_score(self):
        """将得分转换为渲染图像"""
        rounded_score = round(self.stats.score, -1)
        score_str = "{:,}".format(rounded_score)
        self.score_image = self.font.render(score_str, True, self.text_color, self.settings.bg_color)

        # 将得分显示在屏幕右上角
        self.score_rect = self.score_image.get_rect()
        self.score_rect.right = self.screen_rect.right - 20
        self.score_rect.top = 20

    def prep_high_score(self):
        """将最高分转换为渲染图像"""
        high_score = round(self.stats.high_score, -1)
        high_score_str = "{:,}".format(high_score)
        self.high_score_image = self.font.render(
            high_score_str, True, self.text_color, self.settings.bg_color)

        # 将最高分居中显示在屏幕顶部
        self.high_score_rect = self.high_score_image.get_rect()
        self.high_score_rect.centerx = self.screen_rect.centerx
        self.high_score_rect.top = self.screen_rect.top

    def check_high_score(self):
        """检查是否诞生了新的最高分"""
        if self.stats.score > self.stats.high_score:
            self.stats.high_score = self.stats.score
            self.prep_high_score()
            self.prep_level()

    def prep_level(self):
        """将等级转换为渲染图像"""
        level_str = str(self.stats.level)
        self.level_image = self.font.render(
            level_str, True, self.text_color, self.settings.bg_color)

        # 将等级放在得分下方
        self.level_rect = self.level_image.get_rect()
        self.level_rect.right = self.score_rect.right
        self.level_rect.top = self.score_rect.bottom + 10

    def show_score(self):
        """在屏幕上绘制得分、最高分和等级"""
        self.screen.blit(self.score_image, self.score_rect)
        self.screen.blit(self.high_score_image, self.high_score_rect)
        self.screen.blit(self.level_image, self.level_rect)

修复说明 #

1. 将所有方法缩进至Scoreboard类内部（每个方法前添加4个空格），确保它们属于类的成员方法；
2. 在__init__方法末尾添加self.prep_level()，确保游戏启动时就创建level_image和level_rect属性，避免首次调用show_score时出现属性不存在的错误。

内容的提问来源于stack exchange，提问作者Plasmaneer