python实践到入门，外星人项目12章的习题的自我练习

类似于外星人项目第一部分的拓展：

刚开始自学python，外星人项目12章，完成了一架飞船可以在屏幕上左右移动，并且可以开火。因为后面的几道习题是单独的，为了简单，就将其勉强凑一起，忽略一些细节问题。然后综合几道习题，完成火箭的上下左右移动。在此基础上，假设火箭向右端开火的情况。当然要实现向其他方向开火，只需要在相应位置更改就行。

1、主程序文件exercise_test.py（类似于外星人项目中的alien_invasion.py)

import sys
import pygame
from pygame.sprite import Group
import game_functions as gf
from settings import Settings
from rocket import Rocket


def run_game():
	
	#初始化背景设置
	pygame.init()
	#创建一个名为screen的显示窗口
	ai_settings = Settings()
	screen = pygame.display.set_mode((ai_settings.screen_width,
		ai_settings.screen_height))
	
	pygame.display.set_caption("Blue Sky")
	
	#创建火箭
	rocket = Rocket(ai_settings, screen)
	
	#创建一个用于存储子弹的编组
	bullets = Group()
	while True:
		gf.check_events(ai_settings, screen, rocket, bullets)
		rocket.update()
		gf.update_bullets(bullets, ai_settings)

		gf.update_screen(ai_settings, screen, rocket, bullets)
		

run_game()

2、game_function.py

import sys
import pygame
from bullet import Bullet

def check_keydown_events(event, ai_settings, screen, rocket, bullets):
	"""响应按键"""
	if event.key == pygame.K_RIGHT:
		rocket.moving_right = True
	elif event.key == pygame.K_LEFT:
		rocket.moving_left = True
	elif event.key == pygame.K_UP:
		rocket.moving_up = True
	elif event.key == pygame.K_DOWN:
		rocket.moving_down = True
	elif event.key == pygame.K_SPACE:
		#创建一颗子弹，并将其加入到编组bullets中
		if len(bullets) < ai_settings.bullets_allowed:
			new_bullet = Bullet(ai_settings, screen, rocket)
			bullets.add(new_bullet)
		
def check_keyup_events(event, rocket):
	"""响应松开"""
	if event.key == pygame.K_RIGHT:
		rocket.moving_right = False
	elif event.key == pygame.K_LEFT:
		rocket.moving_left = False
	elif event.key == pygame.K_UP:
		rocket.moving_up = False
	elif event.key == pygame.K_DOWN:
		rocket.moving_down = False

def check_events(ai_settings, screen, rocket, bullets):
	"""响应案件和鼠标事件"""
	for event in pygame.event.get():
		if event.type == pygame.QUIT:
			sys.exit()
		elif event.type == pygame.KEYDOWN:
			check_keydown_events(event, ai_settings,screen, 
				rocket, bullets)
				
		elif event.type == pygame.KEYUP:
			check_keyup_events(event, rocket)
				
def update_screen(ai_settings, screen, rocket, bullets):
	"""更新屏幕上的图像，并切换到新屏幕"""
	#每次循环时都重新绘制屏幕
	screen.fill(ai_settings.bg_color)
	#在火箭和外星人后面重绘所有子弹
	for bullet in bullets.sprites():
		bullet.draw_bullet()
	rocket.blitme()
		
	#让最近绘制的屏幕可见
	pygame.display.flip()

def update_bullets(bullets, ai_settings):
	"""更新子弹的位置，并删除已消失的子弹"""
	bullets.update()
	#删除已消失的子弹,利用子弹右边界不能超过屏幕宽度来设定
	for bullet in bullets.copy():
		if bullet.rect.right >= ai_settings.screen_width:
			bullets.remove(bullet)
	#可通过下面代码来检测是否成功
	"""print(len(bullets))"""

3、rocket.py

import pygame

class Rocket():
	def __init__(self, ai_settings, screen):
		#初始化火箭并且设置其初始位置
		self.screen = screen
		self.ai_settings = ai_settings
		#加载火箭图像并获取其外接矩形
		self.image = pygame.image.load('images/rocket.bmp')
		self.rect = self.image.get_rect()
		self.screen_rect = screen.get_rect()
		
		#将每个火箭放在屏幕*
		self.rect.centerx = self.screen_rect.centerx
		self.rect.centery = self.screen_rect.centery
		
		#在飞船的属性center中存储小数值
		self.center = float(self.rect.centerx)
		self.center_up_down = float(self.rect.centery)

		#移动标志
		self.moving_right = False
		self.moving_left = False
		self.moving_up = False
		self.moving_down = False
	def update(self):
		"""根据移动标志调整火箭的位置,右左上下"""
		if self.moving_right and self.rect.right < self.screen_rect.right:
			self.center += self.ai_settings.rocket_speed_factor
		if self.moving_left and self.rect.left > 0:
			self.center -= self.ai_settings.rocket_speed_factor
		if self.moving_up and self.rect.top > 0:
			self.center_up_down -= self.ai_settings.rocket_speed_factor
		if self.moving_down and self.rect.bottom < self.screen_rect.bottom:
			self.center_up_down += self.ai_settings.rocket_speed_factor
			
		#根据self.center更新rect对象
		self.rect.centerx = self.center
		self.rect.centery = self.center_up_down

	def blitme(self):
		"""在指定位置绘制火箭"""
		self.screen.blit(self.image, self.rect)

4、setting.py

class Settings():
	"""创建包含所有设置的类"""
	
	def __init__(self):
		self.screen_width = 800
		self.screen_height = 600
		self.bg_color = (0, 191, 255)
		
		#设置飞船的速度
		self.rocket_speed_factor = 1.5
		#子弹设置
		self.bullet_speed_factor = 1
		self.bullet_width = 15
		self.bullet_height = 3
		self.bullet_color = 60, 60, 60
		self.bullets_allowed = 3

5、bullet.py

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, ai_settings, screen, rocket):
		"""在飞船所在的位置创建一个子弹对象"""
		super().__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, ai_settings.bullet_width, ai_settings.bullet_height)
		self.rect.centerx = rocket.rect.centerx
		self.rect.centery = rocket.rect.centery
		
		#存储用小数点表示的子弹位置
		self.y = float(self.rect.y)
		self.x = float(self.rect.x)
		
		self.color = ai_settings.bullet_color
		self.speed_factor = ai_settings.bullet_speed_factor
		
	def update(self):
		"""向有移动子弹"""
		#更新表示子弹位置的小数值,通过换x、y来决定子弹的方向
		self.x += self.speed_factor
		#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)