【Python编程：从入门到实践】第十四章练习题

14-1  按 P 开始新游戏 ：鉴于游戏《外星人入侵》使用键盘来控制飞船，最好让玩家也能够通过按键来开始游戏。请添加让玩家在按 P 时开始游戏的代码。也许这样做会有所帮助：将 check_play_button() 的一些代码提取出来，放到一个名为start_game() 的函数中，并在 check_play_button()和 check_keydown_events() 中调用这个函数。
14-2  射击练习 ：创建一个矩形，它在屏幕右边缘以固定的速度上下移动。然后，在屏幕左边缘创建一艘飞船，玩家可上下移动该飞船，并射击前述矩形目标。添加一个用于开始游戏的 Play 按钮，在玩家三次未击中目标时结束游戏，并重新显示 Play 按钮，让玩家能够通过单击该按钮来重新开始游戏。
14-3  有一定难度的射击练习 ：以你为完成练习 14-2 而做的工作为基础，让标靶的移动速度随游戏进行而加快，并在玩家单击 Play 按钮时将其重置为初始值。
14-4  历史最高分 ：每当玩家关闭并重新开始游戏《外星人入侵》时，最高分都将被重置。请修复这个问题，调用 sys.exit() 前将最高分写入文件，并当在 GameStats 中初始化最高分时从文件中读取它。
14-6  扩展游戏《外星人入侵》 ：想想如何扩展游戏《外星人入侵》。例如，可让外星人也能够向飞船射击，或者添加盾牌，让飞船躲到它后面，使得只有从两边射来的子弹才能摧毁飞船。另外，还可以使用像 pygame.mixer 这样的模块来添加音效，如爆炸声和射击声。

合并为一个游戏“飞船射击矩形”，效果图如下：

代码：

file.py（存储信息到文件和获取文件的信息）

import pickle
# filename = 'file/stats.pkl'
# 存储信息到文件
def save_file(obj, filename):
	statsObj = load_file(filename)
	if statsObj == 0:
		# 不存在文件时，直接保存字典
		with open(filename, 'wb') as f:
			pickle.dump(obj, f, pickle.HIGHEST_PROTOCOL)
	else:
		# 存在文件时，只修改文件中的最高分
		for key, val in statsObj.items():
			# 获取文件最高分的值（当文件字段不止一个时候使用）
			if key == 'highScore':
				statsObj[key] = obj['highScore']
		obj = statsObj
	with open(filename, 'wb') as f:
		pickle.dump(obj, f, pickle.HIGHEST_PROTOCOL)
	
# 读取信息
def load_file(filename):
	try:
		with open(filename, 'rb') as f:
			return pickle.load(f)
	except FileNotFoundError:
		# 不存在文件则输入错误信息
		msg = "Sorry, the file " + filename + " does not exist."
		print(msg)
		return 0

# obj = {'highScore': 20, 'points': 5}
# obj = {'highScore': 50}
# save_file(obj, filename)
# filedata = load_file(filename)
# print(filedata)

settings.py（定义一些必须的基本属性和初始值）。

Tips：注意最高分“high_score”从文件读取，所以关闭程序再打开也能显示以前的最高分。

import file as f
class Settings():
	def __init__(self):
		self.screen_width = 1000
		self.screen_height = 600
		self.bg_color = (230, 230, 230)
		# 设置矩形尺寸、颜色
		self.rect_width = 50
		self.rect_height = 60
		self.rect_color = (255, 255, 255)
	    # 子弹设置（宽、高、颜色、最大数量）        
		self.bullet_width = 15
		self.bullet_height = 5
		self.bullet_color = 60, 60, 60	
	    # 加快游戏节奏的速度
		self.speedup_scale = 1.1
	    # 分数的提高速度
		self.score_scale = 1.5

		self.initialize_settings()
		# 初始化统计信息
		self.reset_stats()
		# 统计信息文件路径
		self.filename = 'file/stats.pkl'
	    # 游戏刚启动时处于非活动状态
		self.game_active = False
		# 读取文件的最高分，在任何情况下都不应重置最高得分
		statsObj = f.load_file(self.filename)
		if statsObj == 0:
			# 不存在文件则显示最高分0
			highScore = 0
		else:
			for key, val in statsObj.items():
				# 获取文件最高分的值（当文件字段不止一个时候使用）
				if key == 'highScore':
					highScore = val
		self.high_score = highScore	
	     
	def initialize_settings(self):
	    """初始化随游戏进行而变化的设置"""
	    self.ship_move_speed = 1.5
	    self.bullet_speed = 3
	    self.rectangle_move_speed = 0.5	
	    # 记分
	    self.one_points = 50
	def increase_speed(self):
	    """提高速度设置"""
	    self.ship_move_speed *= self.speedup_scale
	    self.bullet_speed *= self.speedup_scale
	    self.rectangle_move_speed *= self.speedup_scale
	    self.one_points = int(self.one_points * self.score_scale)
	def reset_stats(self):
		"""初始化在游戏运行期间可能变化的统计信息"""
		# 可射失的数量
		self.ship_limit = 3
		# 射击分数
		self.score = 0
		# 等级
		self.level = 1
		# 打中多少矩形升一级
		self.level_number = 3

ship.py（创建飞船类，并定义飞船的属性和方法（旋转rotate、缩放scale、更新update（键盘上下键控制上下移动）和绘制draw_ship））。

import pygame
from pygame.sprite import Sprite
class Ship(Sprite):
	def __init__(self, settings, screen):
		super(Ship, self).__init__()
		self.settings = settings
		self.screen = screen
		self.screen_rect = self.screen.get_rect()
		# 引入飞船图片并定位
		self.image = pygame.image.load('../images/ship.png')		
		self.rect = self.image.get_rect()
		self.rect.centery = self.screen_rect.centery
		self.rect.left = 0

		# 在矩形的属性 center 中存储小数值
		self.center = float(self.rect.centery)
		# 移动标志
		self.move_down = False
		self.move_up = False
	def rotate(self, angle):
		# 图片旋转
		self.image = pygame.transform.rotate(self.image, angle)
	def scale(self, multiple):
		# 图片缩放
		self.image = pygame.transform.smoothscale(self.image, (multiple, multiple))
	def update(self):
		if self.move_down and self.rect.bottom < self.screen_rect.bottom:
			self.center += self.settings.ship_move_speed
		if self.move_up and self.rect.top > 0:
			self.center -= self.settings.ship_move_speed
		self.rect.centery = self.center
	def draw_ship(self):
		"""绘制飞船到屏幕"""
		self.screen.blit(self.image, self.rect)

bullet.py（创建子弹类，并定义子弹的属性和方法（更新update（按空格键发射子弹由左到右）和绘制draw_bullet））。

import pygame
from pygame.sprite import Sprite
class Bullet(Sprite):
	""" 一个对飞船发射的子弹进行管理的类 """
	def __init__(self, settings, screen, ship):
		""" 在飞船所处的位置创建一个子弹对象 """
		super(Bullet, self).__init__()
		self.screen = screen
		#  在 (0,0) 处创建一个表示子弹的矩形，再设置正确的位置
		self.rect = pygame.Rect(0, 0, settings.bullet_width, settings.bullet_height)
		self.rect.centery = ship.rect.centery
			# 飞船顶部
		self.rect.left = ship.rect.right
		# 存储用小数表示的子弹位置
		self.x = float(self.rect.x)
		self.color = settings.bullet_color
		self.speed = settings.bullet_speed
	def update(self):
		"""向上移动子弹"""
		# 更新表示子弹位置的小数值（子弹往右）
		self.x += self.speed
		# 更新表示子弹的rect的位置
		self.rect.x = self.x
	def draw_bullet(self):
		"""在屏幕上绘制子弹"""
		pygame.draw.rect(self.screen, self.color, self.rect)

rectangle.py（创建矩形类，并定义矩形的属性和方法（更新update（自动上下移动）和绘制draw_rect））。

import pygame
from pygame.sprite import Sprite
class Rectangle(Sprite):
	def __init__(self, settings, screen):
		super(Rectangle, self).__init__()
		self.settings = settings
		self.screen = screen
		self.screen_rect = screen.get_rect()		
		# 创建rect对象并定位到右边缘顶部
		self.rect = pygame.Rect(0, 0, self.settings.rect_width, self.settings.rect_height)
		self.rect.y = 0
		self.rect.right = self.screen_rect.right
		# 在矩形的属性 center 中存储小数值
		self.center = float(self.rect.centery)
		# 默认先往下移动
		self.move_down = True
	def update(self):
		if self.move_down:
			self.center += self.settings.rectangle_move_speed
			# 到底就往上移动
			if self.rect.bottom >= self.screen_rect.bottom:
				self.move_down = False
		else:
			self.center -= self.settings.rectangle_move_speed
			# 到顶就往下移动
			if self.rect.top <= 0:
				self.move_down = True
		self.rect.centery = self.center
	def draw_rect(self):
		pygame.draw.rect(self.screen, self.settings.rect_color, self.rect)

button.py（创建按钮类，并定义按钮的属性和方法（渲染prep_msg（把字符串渲染成图片）和绘制draw_button））。

import pygame.font
class Button():
	def __init__(self, screen, msg):
		"""初始化按钮的属性"""
		self.screen = screen
		self.screen_rect = screen.get_rect()
		# 设置按钮的尺寸和其他属性
		self.width, self.height = 200, 50
		self.button_color = (216, 30, 6)
		self.text_color = (255, 255, 255)
		self.font = pygame.font.SysFont(None, 48)
		# 创建按钮的rect对象，并使其居中
		self.rect = pygame.Rect(0, 0, self.width, self.height)
		self.rect.center = self.screen_rect.center
		# 按钮的标签只需创建一次
		self.prep_msg(msg)
	def prep_msg(self, msg):
		"""将msg渲染为图像，并使其在按钮上居中"""
		self.msg_image = self.font.render(msg, True, self.text_color, self.button_color)
		self.msg_image_rect = self.msg_image.get_rect()
		self.msg_image_rect.center = self.rect.center
	def draw_button(self):
		# 绘制一个用颜色填充的按钮，再绘制文本
		self.screen.fill(self.button_color, self.rect)
		self.screen.blit(self.msg_image, self.msg_image_rect)

scoreboard.py（创建记分牌类，并定义记分牌的属性和方法（渲染prep_score（把分数渲染成图片）、prep_high_score（把最高分渲染成图片）、prep_level（把等级渲染成图片）、prep_ships（把生命数（飞船）渲染成图片）和显示统计信息show_score））。

import pygame.font
from pygame.sprite import Group
from ship import Ship
class Scoreboard():
	"""显示得分信息的类"""
	def __init__(self, settings, screen):
		"""初始化显示得分涉及的属性"""
		self.screen = screen
		self.screen_rect = screen.get_rect()
		self.settings = settings
		# 显示得分信息时使用的字体设置
		self.text_color = (30, 30, 30)
		self.font = pygame.font.SysFont(None, 30)
		# 飞船缩放值
		self.scaleValue = 20
		# 准备初始得分图像\最高得分\等级
		self.prep_score()
		self.prep_high_score()
		self.prep_level()
		self.prep_ships()
	def prep_score(self):
		"""将得分转换为渲染的图像"""
		rounded_score = int(round(self.settings.score, -1))
		score_str = '{:,}'.format(rounded_score)
		self.score_image = self.font.render(score_str, True, self.text_color)
		# 将得分放在屏幕右上角
		self.score_rect = self.score_image.get_rect()
		self.score_rect.right = self.screen_rect.right -20
		self.score_rect.top = 10
	def prep_high_score(self):
		""" 将最高得分转换为渲染的图像 """
		high_score = int(round(self.settings.high_score, -1))
		high_score_str = "{:,}".format(high_score)
		self.high_score_image = self.font.render(high_score_str, True, self.text_color)
		# 将最高得分放在屏幕顶部中央
		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):
		"""将等级转换为渲染的图像"""
		self.level_image = self.font.render(str(self.settings.level), True,	self.text_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 prep_ships(self):
		""" 显示还余下多少艘飞船 """
		self.ships = Group()
		for ship_number in range(self.settings.ship_limit):
			ship = Ship(self.settings, self.screen)

			# 缩放球大小并赋值位置
			ship.scale(self.scaleValue)
			ship.rect.x = 10 + ship.rect.width * ship_number * 0.5
			ship.rect.y = self.score_rect.top
			self.ships.add(ship)
	def show_score(self):
		"""在屏幕上显示得分"""
		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)
		#  绘制飞船
		self.ships.draw(self.screen)

game_functions.py（放置跟业务逻辑有关的函数）

import sys
import pygame
from rectangle import Rectangle
from bullet import Bullet
import file as f

# 事件
def check_events(settings, screen, ship, play_button, scoreboard, rects, bullets, fireSound):
    """ 响应按键和鼠标事件 """
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
        	save_file(settings)
        	sys.exit()
        elif event.type == pygame.KEYDOWN:
            check_keydown_events(event, settings, screen, ship, scoreboard, rects, bullets, fireSound)
        elif event.type == pygame.KEYUP:
            check_keyup_events(event, ship)
        elif event.type == pygame.MOUSEBUTTONDOWN:
            mouse_x, mouse_y = pygame.mouse.get_pos()
            check_play_button(settings, play_button, scoreboard, rects, bullets, mouse_x, mouse_y)
def check_keydown_events(event, settings, screen, ship, scoreboard, rects, bullets, fireSound):
    """ 响应按键 """
    if event.key == pygame.K_DOWN:
        ship.move_down = True
    elif event.key == pygame.K_UP:
        ship.move_up = True
    elif event.key == pygame.K_SPACE:
    	fireSound.play()
    	# 点击空格键创建一颗子弹
    	fire_bullet(settings, screen, ship, bullets)
    elif event.key == pygame.K_p:
        start_game(settings, scoreboard, rects, bullets)
    elif event.key == pygame.K_q:
    	save_file(settings)
    	sys.exit()
def check_keyup_events(event, ship):
    """ 响应松开 """
    if event.key == pygame.K_DOWN:
        ship.move_down = False
    elif event.key == pygame.K_UP:
        ship.move_up = False
def check_play_button(settings, play_button, scoreboard, rects, bullets, mouse_x, mouse_y):
    """在玩家单击Play按钮时开始新游戏"""
    button_clicked = play_button.rect.collidepoint(mouse_x, mouse_y)
    if button_clicked and not settings.game_active:
        start_game(settings, scoreboard, rects, bullets)
def start_game(settings, scoreboard, rects, bullets):
    """开始游戏"""
    # 重置游戏设置
    settings.initialize_settings()
    # 隐藏光标
    pygame.mouse.set_visible(False)
    # 重置游戏统计信息
    settings.reset_stats()        
    settings.game_active = True
    # 重置记分牌图像
    scoreboard.prep_score()
    scoreboard.prep_high_score()
    scoreboard.prep_level()
    scoreboard.prep_ships()
    # 清空矩形列表和子弹列表
    rects.empty()
    bullets.empty()

# 文件
def save_file(settings):
	obj = {'highScore': settings.high_score}
	f.save_file(obj, settings.filename)

# 矩形
def create_rect(settings, screen, rects):
	"""当没有矩形才能创建一个矩形"""
	if len(rects) == 0:
		new_rect = Rectangle(settings, screen)
		rects.add(new_rect)

# 子弹
def fire_bullet(settings, screen, ship, bullets):
	"""当没有子弹才能创建一颗子弹"""
	if len(bullets) == 0:
		new_bullet = Bullet(settings, screen, ship)
		bullets.add(new_bullet)
def update_bullets(settings, screen, scoreboard, rects, bullets, explosiveSound):
    """更新子弹的位置，并删除已消失的子弹"""
    # 更新子弹的位置
    bullets.update()

    # 删除已消失的子弹并同时更新飞船的生命
    for bullet in bullets.copy():
        if bullet.rect.right > screen.get_rect().right:
            bullets.remove(bullet)
            settings.ship_limit -= 1
            scoreboard.prep_ships()
        # 当三条命都没了，游戏结束
        if settings.ship_limit == 0:
        	settings.game_active = False

    # 子弹打到矩形
    check_bullet_rect_collisions(settings, scoreboard, rects, bullets, explosiveSound)
def check_bullet_rect_collisions(settings, scoreboard, rects, bullets, explosiveSound):
	# 检查是否有子弹击中了矩形
	# 如果是这样，就删除相应的子弹和矩形（两个True分别删除子弹和矩形，不删除就改为False）
	collisions = pygame.sprite.groupcollide(bullets, rects, True, True)
	if collisions:
		# pygame.mixer.music.play()
		explosiveSound.play()
		# 计算打击到多少矩形（这里一直只有一个），并计算分数并渲染
		for rects in collisions.values():
			settings.score += settings.one_points * len(rects)
			scoreboard.prep_score()
	    # 渲染最高分
		check_high_score(settings, scoreboard)
	    # 等达到等级数量升级并渲染新等级
		settings.level_number -= 1
		if settings.level_number == 0:
			settings.increase_speed()
			settings.level += 1
			scoreboard.prep_level()
	    	# 还原为3（同settings一致）
			settings.level_number = 3

# 分数
def check_high_score(settings, scoreboard):
    """检查是否诞生了新的最高得分"""
    if settings.score > settings.high_score:
        settings.high_score = settings.score
        scoreboard.prep_high_score()

# 屏幕
def update_screen(settings, screen, ship, play_button, scoreboard, rects, bullets):
	""" 更新屏幕上的图像，并切换到新屏幕 """
	# 每次循环时都重绘屏幕
	screen.fill(settings.bg_color)
	# 绘制飞船到屏幕
	ship.draw_ship()
	# 绘制矩形到屏幕
	create_rect(settings, screen, rects)
	for rect in rects.sprites():
		rect.draw_rect()
	# 绘制子弹到屏幕 
	for bullet in bullets.sprites():
		bullet.draw_bullet()
	# 渲染记分牌信息
	scoreboard.show_score()
	# 如果游戏处于非活动状态，就绘制 Play 按钮
	if not settings.game_active:
		play_button.draw_button()
	# 让最近绘制的屏幕可见
	pygame.display.flip()

shootingrectangle.py（程序主函数）

Tips：由于“pygame.mixer.music”一次只能播放一个音乐，为了满足播放背景音乐同时播放音效，需要混合使用“pygame.mixer.Sound”（Sound不能使用mp3）。

import pygame
from pygame.sprite import Group
from settings import Settings
from button import Button
from ship import Ship
from bullet import Bullet
import game_functions as gf
from scoreboard import Scoreboard

def run_game():
	pygame.init()
	# 初始化全部音频，并加载爆炸声音乐
	pygame.mixer.init()
		# 等待1s
	pygame.time.delay(1000)
	pygame.mixer.music.load('file/bgsound.mp3')
		# -1代表无限循环（背景音乐）
	pygame.mixer.music.play(-1)
		# 爆炸声
	explosiveSound = pygame.mixer.Sound('file/explosiveSound.wav')
		# 枪声
	fireSound = pygame.mixer.Sound('file/fireSound.wav')

	settings = Settings()
	screen = pygame.display.set_mode((settings.screen_width, settings.screen_height))
	# 全屏显示
	# screen = pygame.display.set_mode((0, 0), pygame.FULLSCREEN)
	pygame.display.set_caption('射击矩形')
	# 创建Play按钮
	play_button = Button(screen, 'Play')

	# 创建飞船、矩形、子弹
	ship = Ship(settings, screen)
	ship.rotate(-90)
	# 创建子弹的编组
	bullets = Group()
	rects = Group()
	# 创建记分牌
	scoreboard = Scoreboard(settings, screen)

	while True:
		# 检查玩家输入（不加会导致一直加载）
		gf.check_events(settings, screen, ship, play_button, scoreboard, rects, bullets, fireSound)
		if settings.game_active:
			# 更新飞船位置
			ship.update()
			# 更新矩形位置
			rects.update()
			# 更新子弹位置
			gf.update_bullets(settings, screen, scoreboard, rects, bullets, explosiveSound)
		# 更新屏幕信息
		gf.update_screen(settings, screen, ship, play_button, scoreboard, rects, bullets)

run_game()