八、計分，建立一個scoreboard.py的檔案

1、顯示分數，在螢幕上顯示最高分，等級和剩餘的飛船數，

在正上方顯示最高分，右上方顯示分數

2、建立記分牌，用於計算得到的分數

3、顯示等級。在外星人消滅後，提高等級

程式碼如下

import pygame.font
from pygame.sprite import Group
from ship import Ship

class Scoreboard():
    #顯示得分資訊的類
    def __init__(self,ai_settings,screen,stats):
        #初始化顯示得分涉及的屬性
        self.screen = screen
        self.screen_rect = screen.get_rect()
        self.ai_settings = ai_settings
        self.stats = stats
        #顯示得分資訊時使用的字型設定
        self.text_color = (30,30,30)
        self.font = pygame.font.SysFont(None,48)

        #準備初始得分影象包含最高得分
        self.prep_score()
        self.prep_high_score()
        self.prep_level()
        self.prep_ships()
    def prep_score(self):
        #將得分轉化為一幅渲染的圖片
        #round的第二個實參是將stats.score值整到10的整數倍
        rounded_score = int(round(self.stats.score,-1))
        #一個字串格式設定指令，在數值中插入逗號
        score_str = "{:,}".format(rounded_score)
        #將字串傳遞給建立影象的render()
        self.score_image = self.font.render(score_str,True,self.text_color,self.ai_settings.bg_color)

        #將得分放在螢幕右上角
        self.score_rect = self.score_image.get_rect()
        self.score_rect.right = self.screen_rect.right -20
        #上邊緣與螢幕相距20畫素
        self.score_rect.top = 20

    def prep_high_score(self):
        #將最高得分轉化為渲染的影象
        high_score = int(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.ai_settings.bg_color)
        #將最高得分放在螢幕頂部中央
        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.score_rect.top

    def prep_level(self):
        #將等級轉換為渲染的影象
        self.level_image = self.font.render(str(self.stats.level),True,self.text_color,self.ai_settings.bg_color)

        #將等級放在得分下方
        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 prep_ships(self):
        #顯示還剩餘多少艘飛船
        self.ships = Group()
        for ship_number in range(self.stats.ships_left):
            ship = Ship(self.ai_settings,self.screen)
            ship .rect.x = 10 + ship_number * ship.rect.width
            ship.rect.y = 10
            self.ships.add(ship)




    def show_score(self):
        #在螢幕上顯示飛船和得分
        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)
        #繪製飛船
        self.ships.draw(self.screen)