python应用篇之外星人入侵项目——总结

前言

  经过十几篇文章的介绍，我们《外星人入侵》的项目总算全部介绍完毕。实现了全部的功能。这个项目是来自Eric Matthes编著的《Python编程从入门到实践书中项目。不过，本人是通过一定的特色，通过我学习项目的方式来给大家介绍这个项目。从环境搭建到后面一步步的实现。当然，随着项目的不断深入，代码的量越来越大，为了方便大家的阅读，我们只是将实现功能对应的代码方法进行了书写。今天，我们给出大家该项目的完整代码，给大家一个完整的效果。不过还是强烈读者从这个项目的开始阅读。这样，相信会对你获益匪浅。如果只是简单的将本文中的所有代码粘贴一遍，没有任何的用，可能你连这个项目的整个框架都不清楚。

项目概括

  我们通过《外星人入侵》项目，需要我们使用pygame包来开发一款2D游戏，它在玩家没消灭一群向下移的外星人后，都将玩家提高一个等级；而等级越高，游戏的节奏越快，难度越大。通过这个项目，我们需要具备pygame的2D游戏所需的技能。
  首先我们给大家看一下我们整个项目的架构：

  我们的项目首先是武装飞船实现，我们通过四篇文章将其实现。其次是通过五篇文章实现外星人的功能；最后通过三篇文章实现记分的部分。接下来，我们讲给大家呈现本项目的全部完整代码；

完整代码

0、项目中需要的图片

  飞船图片：

  外星人的图片：

1、alien.py的实现

import pygame
from pygame.sprite import Sprite

class Alien(Sprite):
    """A class to represent a single alien in the fleet."""

    def __init__(self, ai_settings, screen):
        """Initialize the alien, and set its starting position."""
        super(Alien, self).__init__()
        self.screen = screen
        self.ai_settings = ai_settings

        # Load the alien image, and set its rect attribute.
        self.image = pygame.image.load('images/alien.bmp')
        self.rect = self.image.get_rect()

        # Start each new alien near the top left of the screen.
        self.rect.x = self.rect.width
        self.rect.y = self.rect.height

        # Store the alien's exact position.
        self.x = float(self.rect.x)
        
    def check_edges(self):
        """Return True if alien is at edge of screen."""
        screen_rect = self.screen.get_rect()
        if self.rect.right >= screen_rect.right:
            return True
        elif self.rect.left <= 0:
            return True
        
    def update(self):
        """Move the alien right or left."""
        self.x += (self.ai_settings.alien_speed_factor *
                        self.ai_settings.fleet_direction)
        self.rect.x = self.x

    def blitme(self):
        """Draw the alien at its current location."""
        self.screen.blit(self.image, self.rect)

2、alien_invasion.py的实现

import pygame
from pygame.sprite import Group

from settings import Settings
from game_stats import GameStats
from scoreboard import Scoreboard
from button import Button
from ship import Ship
import game_functions as gf

def run_game():
    # Initialize pygame, settings, and screen object.
    pygame.init()
    ai_settings = Settings()
    screen = pygame.display.set_mode(
        (ai_settings.screen_width, ai_settings.screen_height))
    pygame.display.set_caption("Alien Invasion")
    
    # Make the Play button.
    play_button = Button(ai_settings, screen, "Play")
    
    # Create an instance to store game statistics, and a scoreboard.
    stats = GameStats(ai_settings)
    sb = Scoreboard(ai_settings, screen, stats)
    
    # Set the background color.
    bg_color = (230, 230, 230)
    
    # Make a ship, a group of bullets, and a group of aliens.
    ship = Ship(ai_settings, screen)
    bullets = Group()
    aliens = Group()
    
    # Create the fleet of aliens.
    gf.create_fleet(ai_settings, screen, ship, aliens)

    # Start the main loop for the game.
    while True:
        gf.check_events(ai_settings, screen, stats, sb, play_button, ship,
            aliens, bullets)
        
        if stats.game_active:
            ship.update()
            gf.update_bullets(ai_settings, screen, stats, sb, ship, aliens,
                bullets)
            gf.update_aliens(ai_settings, screen, stats, sb, ship, aliens,
                bullets)
        
        gf.update_screen(ai_settings, screen, stats, sb, ship, aliens,
            bullets, play_button)

run_game()

3、bullet.py的实现

import pygame
from pygame.sprite import Sprite

class Bullet(Sprite):
    """A class to manage bullets fired from the ship."""

    def __init__(self, ai_settings, screen, ship):
        """Create a bullet object, at the ship's current position."""
        super(Bullet, self).__init__()
        self.screen = screen

        # Create bullet rect at (0, 0), then set correct position.
        self.rect = pygame.Rect(0, 0, ai_settings.bullet_width,
            ai_settings.bullet_height)
        self.rect.centerx = ship.rect.centerx
        self.rect.top = ship.rect.top
        
        # Store a decimal value for the bullet's position.
        self.y = float(self.rect.y)

        self.color = ai_settings.bullet_color
        self.speed_factor = ai_settings.bullet_speed_factor

    def update(self):
        """Move the bullet up the screen."""
        # Update the decimal position of the bullet.
        self.y -= self.speed_factor
        # Update the rect position.
        self.rect.y = self.y

    def draw_bullet(self):
        """Draw the bullet to the screen."""
        pygame.draw.rect(self.screen, self.color, self.rect)

4、button.py的实现

import pygame.font

class Button():

    def __init__(self, ai_settings, screen, msg):
        """Initialize button attributes."""
        self.screen = screen
        self.screen_rect = screen.get_rect()
        
        # Set the dimensions and properties of the button.
        self.width, self.height = 200, 50
        self.button_color = (0, 255, 0)
        self.text_color = (255, 255, 255)
        self.font = pygame.font.SysFont(None, 48)
        
        # Build the button's rect object, and center it.
        self.rect = pygame.Rect(0, 0, self.width, self.height)
        self.rect.center = self.screen_rect.center
        
        # The button message only needs to be prepped once.
        self.prep_msg(msg)

    def prep_msg(self, msg):
        """Turn msg into a rendered image, and center text on the button."""
        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):
        # Draw blank button, then draw message.
        self.screen.fill(self.button_color, self.rect)
        self.screen.blit(self.msg_image, self.msg_image_rect)

5、game_functions.py的实现

import sys
from time import sleep

import pygame

from bullet import Bullet
from alien import Alien

def check_keydown_events(event, ai_settings, screen, ship, bullets):
    """Respond to keypresses."""
    if event.key == pygame.K_RIGHT:
        ship.moving_right = True
    elif event.key == pygame.K_LEFT:
        ship.moving_left = True
    elif event.key == pygame.K_SPACE:
        fire_bullet(ai_settings, screen, ship, bullets)
    elif event.key == pygame.K_q:
        sys.exit()
        
def check_keyup_events(event, ship):
    """Respond to key releases."""
    if event.key == pygame.K_RIGHT:
        ship.moving_right = False
    elif event.key == pygame.K_LEFT:
        ship.moving_left = False

def check_events(ai_settings, screen, stats, sb, play_button, ship, aliens,
        bullets):
    """Respond to keypresses and mouse events."""
    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, ship, bullets)
        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(ai_settings, screen, stats, sb, play_button,
                ship, aliens, bullets, mouse_x, mouse_y)
            
def check_play_button(ai_settings, screen, stats, sb, play_button, ship,
        aliens, bullets, mouse_x, mouse_y):
    """Start a new game when the player clicks Play."""
    button_clicked = play_button.rect.collidepoint(mouse_x, mouse_y)
    if button_clicked and not stats.game_active:
        # Reset the game settings.
        ai_settings.initialize_dynamic_settings()
        
        # Hide the mouse cursor.
        pygame.mouse.set_visible(False)
        
        # Reset the game statistics.
        stats.reset_stats()
        stats.game_active = True
        
        # Reset the scoreboard images.
        sb.prep_score()
        sb.prep_high_score()
        sb.prep_level()
        sb.prep_ships()
        
        # Empty the list of aliens and bullets.
        aliens.empty()
        bullets.empty()
        
        # Create a new fleet and center the ship.
        create_fleet(ai_settings, screen, ship, aliens)
        ship.center_ship()

def fire_bullet(ai_settings, screen, ship, bullets):
    """Fire a bullet, if limit not reached yet."""
    # Create a new bullet, add to bullets group.
    if len(bullets) < ai_settings.bullets_allowed:
        new_bullet = Bullet(ai_settings, screen, ship)
        bullets.add(new_bullet)

def update_screen(ai_settings, screen, stats, sb, ship, aliens, bullets,
        play_button):
    """Update images on the screen, and flip to the new screen."""
    # Redraw the screen, each pass through the loop.
    screen.fill(ai_settings.bg_color)
    
    # Redraw all bullets, behind ship and aliens.
    for bullet in bullets.sprites():
        bullet.draw_bullet()
    ship.blitme()
    aliens.draw(screen)
    
    # Draw the score information.
    sb.show_score()
    
    # Draw the play button if the game is inactive.
    if not stats.game_active:
        play_button.draw_button()

    # Make the most recently drawn screen visible.
    pygame.display.flip()
    
def update_bullets(ai_settings, screen, stats, sb, ship, aliens, bullets):
    """Update position of bullets, and get rid of old bullets."""
    # Update bullet positions.
    bullets.update()

    # Get rid of bullets that have disappeared.
    for bullet in bullets.copy():
        if bullet.rect.bottom <= 0:
            bullets.remove(bullet)
            
    check_bullet_alien_collisions(ai_settings, screen, stats, sb, ship,
        aliens, bullets)
        
def check_high_score(stats, sb):
    """Check to see if there's a new high score."""
    if stats.score > stats.high_score:
        stats.high_score = stats.score
        sb.prep_high_score()
            
def check_bullet_alien_collisions(ai_settings, screen, stats, sb, ship,
        aliens, bullets):
    """Respond to bullet-alien collisions."""
    # Remove any bullets and aliens that have collided.
    collisions = pygame.sprite.groupcollide(bullets, aliens, True, True)
    
    if collisions:
        for aliens in collisions.values():
            stats.score += ai_settings.alien_points * len(aliens)
            sb.prep_score()
        check_high_score(stats, sb)
    
    if len(aliens) == 0:
        # If the entire fleet is destroyed, start a new level.
        bullets.empty()
        ai_settings.increase_speed()
        
        # Increase level.
        stats.level += 1
        sb.prep_level()
        
        create_fleet(ai_settings, screen, ship, aliens)
    
def check_fleet_edges(ai_settings, aliens):
    """Respond appropriately if any aliens have reached an edge."""
    for alien in aliens.sprites():
        if alien.check_edges():
            change_fleet_direction(ai_settings, aliens)
            break
        
def change_fleet_direction(ai_settings, aliens):
    """Drop the entire fleet, and change the fleet's direction."""
    for alien in aliens.sprites():
        alien.rect.y += ai_settings.fleet_drop_speed
    ai_settings.fleet_direction *= -1
    
def ship_hit(ai_settings, screen, stats, sb, ship, aliens, bullets):
    """Respond to ship being hit by alien."""
    if stats.ships_left > 0:
        # Decrement ships_left.
        stats.ships_left -= 1
        
        # Update scoreboard.
        sb.prep_ships()
        
    else:
        stats.game_active = False
        pygame.mouse.set_visible(True)
    
    # Empty the list of aliens and bullets.
    aliens.empty()
    bullets.empty()
    
    # Create a new fleet, and center the ship.
    create_fleet(ai_settings, screen, ship, aliens)
    ship.center_ship()
    
    # Pause.
    sleep(0.5)
    
def check_aliens_bottom(ai_settings, screen, stats, sb, ship, aliens,
        bullets):
    """Check if any aliens have reached the bottom of the screen."""
    screen_rect = screen.get_rect()
    for alien in aliens.sprites():
        if alien.rect.bottom >= screen_rect.bottom:
            # Treat this the same as if the ship got hit.
            ship_hit(ai_settings, screen, stats, sb, ship, aliens, bullets)
            break
            
def update_aliens(ai_settings, screen, stats, sb, ship, aliens, bullets):
    """
    Check if the fleet is at an edge,
      then update the postions of all aliens in the fleet.
    """
    check_fleet_edges(ai_settings, aliens)
    aliens.update()
    
    # Look for alien-ship collisions.
    if pygame.sprite.spritecollideany(ship, aliens):
        ship_hit(ai_settings, screen, stats, sb, ship, aliens, bullets)

    # Look for aliens hitting the bottom of the screen.
    check_aliens_bottom(ai_settings, screen, stats, sb, ship, aliens, bullets)
            
def get_number_aliens_x(ai_settings, alien_width):
    """Determine the number of aliens that fit in a row."""
    available_space_x = ai_settings.screen_width - 2 * alien_width
    number_aliens_x = int(available_space_x / (2 * alien_width))
    return number_aliens_x
    
def get_number_rows(ai_settings, ship_height, alien_height):
    """Determine the number of rows of aliens that fit on the screen."""
    available_space_y = (ai_settings.screen_height -
                            (3 * alien_height) - ship_height)
    number_rows = int(available_space_y / (2 * alien_height))
    return number_rows
    
def create_alien(ai_settings, screen, aliens, alien_number, row_number):
    """Create an alien, and place it in the row."""
    alien = Alien(ai_settings, screen)
    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
    aliens.add(alien)

def create_fleet(ai_settings, screen, ship, aliens):
    """Create a full fleet of aliens."""
    # Create an alien, and find number of aliens in a row.
    alien = Alien(ai_settings, screen)
    number_aliens_x = get_number_aliens_x(ai_settings, alien.rect.width)
    number_rows = get_number_rows(ai_settings, ship.rect.height,
        alien.rect.height)
    
    # Create the fleet of aliens.
    for row_number in range(number_rows):
        for alien_number in range(number_aliens_x):
            create_alien(ai_settings, screen, aliens, alien_number,
                row_number)

6、game_stats.py的实现

class GameStats():
    """Track statistics for Alien Invasion."""
    
    def __init__(self, ai_settings):
        """Initialize statistics."""
        self.ai_settings = ai_settings
        self.reset_stats()
        
        # Start game in an inactive state.
        self.game_active = False
        
        # High score should never be reset.
        self.high_score = 0
        
    def reset_stats(self):
        """Initialize statistics that can change during the game."""
        self.ships_left = self.ai_settings.ship_limit
        self.score = 0
        self.level = 1

7、scoreboard.py的实现

import pygame.font
from pygame.sprite import Group

from ship import Ship

class Scoreboard():
    """A class to report scoring information."""

    def __init__(self, ai_settings, screen, stats):
        """Initialize scorekeeping attributes."""
        self.screen = screen
        self.screen_rect = screen.get_rect()
        self.ai_settings = ai_settings
        self.stats = 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()
        self.prep_level()
        self.prep_ships()

    def prep_score(self):
        """Turn the score into a rendered image."""
        rounded_score = int(round(self.stats.score, -1))
        score_str = "{:,}".format(rounded_score)
        self.score_image = self.font.render(score_str, True, self.text_color,
            self.ai_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 = 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)
                
        # 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.score_rect.top
        
    def prep_level(self):
        """Turn the level into a rendered image."""
        self.level_image = self.font.render(str(self.stats.level), True,
                self.text_color, self.ai_settings.bg_color)
        
        # Position 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 prep_ships(self):
        """Show how many ships are left."""
        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):
        """Draw score 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)
        # Draw ships.
        self.ships.draw(self.screen)

8、settings.py的实现

class Settings():
    """A class to store all settings for Alien Invasion."""

    def __init__(self):
        """Initialize the game's static settings."""
        # Screen settings.
        self.screen_width = 1200
        self.screen_height = 800
        self.bg_color = (230, 230, 230)
        
        # Ship settings.
        self.ship_limit = 3
            
        # Bullet settings.
        self.bullet_width = 3
        self.bullet_height = 15
        self.bullet_color = 60, 60, 60
        self.bullets_allowed = 3
        
        # Alien settings.
        self.fleet_drop_speed = 10
            
        # How quickly the game speeds up.
        self.speedup_scale = 1.1
        # How quickly the alien point values increase.
        self.score_scale = 1.5
    
        self.initialize_dynamic_settings()

    def initialize_dynamic_settings(self):
        """Initialize settings that change throughout the game."""
        self.ship_speed_factor = 1.5
        self.bullet_speed_factor = 3
        self.alien_speed_factor = 1
        
        # Scoring.
        self.alien_points = 50
    
        # fleet_direction of 1 represents right, -1 represents left.
        self.fleet_direction = 1
        
    def increase_speed(self):
        """Increase speed settings and alien point values."""
        self.ship_speed_factor *= self.speedup_scale
        self.bullet_speed_factor *= self.speedup_scale
        self.alien_speed_factor *= self.speedup_scale
        
        self.alien_points = int(self.alien_points * self.score_scale)

9、ship.py的实现

import pygame
from pygame.sprite import Sprite

class Ship(Sprite):

    def __init__(self, ai_settings, screen):
        """Initialize the ship, and set its starting position."""
        super(Ship, self).__init__()
        self.screen = screen
        self.ai_settings = ai_settings

        # Load the ship image, and get its rect.
        self.image = pygame.image.load('images/ship.bmp')
        self.rect = self.image.get_rect()
        self.screen_rect = screen.get_rect()

        # Start each new ship at the bottom center of the screen.
        self.rect.centerx = self.screen_rect.centerx
        self.rect.bottom = self.screen_rect.bottom
        
        # Store a decimal value for the ship's center.
        self.center = float(self.rect.centerx)
        
        # Movement flags.
        self.moving_right = False
        self.moving_left = False
        
    def center_ship(self):
        """Center the ship on the screen."""
        self.center = self.screen_rect.centerx
        
    def update(self):
        """Update the ship's position, based on movement flags."""
        # Update the ship's center value, not the rect.
        if self.moving_right and self.rect.right < self.screen_rect.right:
            self.center += self.ai_settings.ship_speed_factor
        if self.moving_left and self.rect.left > 0:
            self.center -= self.ai_settings.ship_speed_factor
            
        # Update rect object from self.center.
        self.rect.centerx = self.center

    def blitme(self):
        """Draw the ship at its current location."""
        self.screen.blit(self.image, self.rect)

  本游戏项目最后的游戏效果如图所示：

  这就是本文的完整代码以及项目的整体架构，希望读者学完之后可以有一个清晰的认知，对自己的Python基础知识的应用有一个初步的认知。

每个功能实现过程

1、武装飞船功能实现

[1]. 武装飞船(上)
[2]. 武装飞船(中)
[3]. 武装飞船(下)
[4]. 武装飞船(完)

2、外星人功能实现

[1]. 外星人(上)
[2]. 外星人(中)
[3]. 外星人(下)
[4]. 外星人(完)
[5]. 外星人(完结)

3、记分功能的实现

[1]. 记分(上)
[2]. 记分(中)
[3]. 记分(完)
  这就是我们本项目每个功能实现的详情，大家可以认真阅读，对大家一定有所帮助。

总结

  本文给大家总结了《外星人入侵》项目，从需求分析，到代码结构，以及给出了本项目的完整代码以及最终的效果图。最后贵吗总结了前面每个功能实现的文章链接，方便大家阅读。Python是一门注重实际操作的语言，它是众多编程语言中最简单，也是最好入门的。当你把这门语言学会了，再去学习java、go以及C语言就比较简单了。当然，Python也是一门热门语言，对于人工智能的实现有着很大的帮助，因此，值得大家花时间去学习。生命不息，奋斗不止，我们每天努力，好好学习，不断提高自己的能力，相信自己一定会学有所获。加油！！！