我正在学习面向对象的Python并理解类的主要原理并从类创建对象但是我需要解释一下Re：下面的pygame代码。我正在努力了解创建精灵列表时发生的事情以及创建球对象的代码下的两行代码（allsprites.add等）。换句话说，什么是精灵，为什么创建它们的列表？为什么球对象本身不是从类中创建的？为什么需要将它添加到精灵列表？这是怎么回事？任何解释都将不胜感激。
"""
Sample Breakout Game
Sample Python/Pygame Programs
Simpson College Computer Science
http://programarcadegames.com/
http://simpson.edu/computer-science/
"""
# --- Import libraries used for this program
import math
import pygame
# Define some colors
black = (0, 0, 0)
white = (255, 255, 255)
blue = (0, 0, 255)
# Size of break-out blocks
block_width = 23
block_height = 15
class Block(pygame.sprite.Sprite):
"""This class represents each block that will get knocked out by the ball
It derives from the "Sprite" class in Pygame """
def __init__(self, color, x, y):
""" Constructor. Pass in the color of the block,
and its x and y position. """
# Call the parent class (Sprite) constructor
pygame.sprite.Sprite.__init__(self)
# Create the image of the block of appropriate size
# The width and height are sent as a list for the first parameter.
self.image = pygame.Surface([block_width, block_height])
# Fill the image with the appropriate color
self.image.fill(color)
# Fetch the rectangle object that has the dimensions of the image
self.rect = self.image.get_rect()
# Move the top left of the rectangle to x,y.
# This is where our block will appear..
self.rect.x = x
self.rect.y = y
class Ball(pygame.sprite.Sprite):
""" This class represents the ball
It derives from the "Sprite" class in Pygame """
# Speed in pixels per cycle
speed = 10.0
# Floating point representation of where the ball is
x = 0.0
y = 180.0
# Direction of ball (in degrees)
direction = 200
width = 10
height = 10
# Constructor. Pass in the color of the block, and its x and y position
def __init__(self):
# Call the parent class (Sprite) constructor
pygame.sprite.Sprite.__init__(self)
# Create the image of the ball
self.image = pygame.Surface([self.width, self.height])
# Color the ball
self.image.fill(white)
# Get a rectangle object that shows where our image is
self.rect = self.image.get_rect()
# Get attributes for the height/width of the screen
self.screenheight = pygame.display.get_surface().get_height()
self.screenwidth = pygame.display.get_surface().get_width()
def bounce(self, diff):
""" This function will bounce the ball
off a horizontal surface (not a vertical one) """
self.direction = (180 - self.direction) % 360
self.direction -= diff
def update(self):
""" Update the position of the ball. """
# Sine and Cosine work in degrees, so we have to convert them
direction_radians = math.radians(self.direction)
# Change the position (x and y) according to the speed and direction
self.x += self.speed * math.sin(direction_radians)
self.y -= self.speed * math.cos(direction_radians)
# Move the image to where our x and y are
self.rect.x = self.x
self.rect.y = self.y
# Do we bounce off the top of the screen?
if self.y <= 0:
self.bounce(0)
self.y = 1
# Do we bounce off the left of the screen?
if self.x <= 0:
self.direction = (360 - self.direction) % 360
self.x = 1
# Do we bounce of the right side of the screen?
if self.x > self.screenwidth - self.width:
self.direction = (360 - self.direction) % 360
self.x = self.screenwidth - self.width - 1
# Did we fall off the bottom edge of the screen?
if self.y > 600:
return True
else:
return False
class Player(pygame.sprite.Sprite):
""" This class represents the bar at the bottom that the player controls. """
def __init__(self):
""" Constructor for Player. """
# Call the parent's constructor
pygame.sprite.Sprite.__init__(self)
self.width = 75
self.height = 15
self.image = pygame.Surface([self.width, self.height])
self.image.fill((white))
# Make our top-left corner the passed-in location.
self.rect = self.image.get_rect()
self.screenheight = pygame.display.get_surface().get_height()
self.screenwidth = pygame.display.get_surface().get_width()
self.rect.x = 0
self.rect.y = self.screenheight-self.height
def update(self):
""" Update the player position. """
# Get where the mouse is
pos = pygame.mouse.get_pos()
# Set the left side of the player bar to the mouse position
self.rect.x = pos[0]
# Make sure we don't push the player paddle
# off the right side of the screen
if self.rect.x > self.screenwidth - self.width:
self.rect.x = self.screenwidth - self.width
# Call this function so the Pygame library can initialize itself
pygame.init()
# Create an 800x600 sized screen
screen = pygame.display.set_mode([800, 600])
# Set the title of the window
pygame.display.set_caption('Breakout')
# Enable this to make the mouse disappear when over our window
pygame.mouse.set_visible(0)
# This is a font we use to draw text on the screen (size 36)
font = pygame.font.Font(None, 36)
# Create a surface we can draw on
background = pygame.Surface(screen.get_size())
# Create sprite lists
blocks = pygame.sprite.Group()
balls = pygame.sprite.Group()
allsprites = pygame.sprite.Group()
# Create the player paddle object
player = Player()
allsprites.add(player)
# Create the ball
ball = Ball()
allsprites.add(ball)
balls.add(ball)
# The top of the block (y position)
top = 80
# Number of blocks to create
blockcount = 32
# --- Create blocks
# Five rows of blocks
for row in range(5):
# 32 columns of blocks
for column in range(0, blockcount):
# Create a block (color,x,y)
block = Block(blue, column * (block_width + 2) + 1, top)
blocks.add(block)
allsprites.add(block)
# Move the top of the next row down
top += block_height + 2
# Clock to limit speed
clock = pygame.time.Clock()
# Is the game over?
game_over = False
# Exit the program?
exit_program = False
# Main program loop
while exit_program != True:
# Limit to 30 fps
clock.tick(30)
# Clear the screen
screen.fill(black)
# Process the events in the game
for event in pygame.event.get():
if event.type == pygame.QUIT:
exit_program = True
# Update the ball and player position as long
# as the game is not over.
if not game_over:
# Update the player and ball positions
player.update()
game_over = ball.update()
# If we are done, print game over
if game_over:
text = font.render("Game Over", True, white)
textpos = text.get_rect(centerx=background.get_width()/2)
textpos.top = 300
screen.blit(text, textpos)
# See if the ball hits the player paddle
if pygame.sprite.spritecollide(player, balls, False):
# The 'diff' lets you try to bounce the ball left or right
# depending where on the paddle you hit it
diff = (player.rect.x + player.width/2) - (ball.rect.x+ball.width/2)
# Set the ball's y position in case
# we hit the ball on the edge of the paddle
ball.rect.y = screen.get_height() - player.rect.height - ball.rect.height - 1
ball.bounce(diff)
# Check for collisions between the ball and the blocks
deadblocks = pygame.sprite.spritecollide(ball, blocks, True)
# If we actually hit a block, bounce the ball
if len(deadblocks) > 0:
ball.bounce(0)
# Game ends if all the blocks are gone
if len(blocks) == 0:
game_over = True
# Draw Everything
allsprites.draw(screen)
# Flip the screen and show what we've drawn
pygame.display.flip()
pygame.quit()
答案 0 :(得分：1)
你没有需要将球和块添加到精灵列表 - 这只是为了方便。你可以手动检查每个球的碰撞，但是更容易告诉pygame为你检查它们
# See if the ball hits the player paddle
if pygame.sprite.spritecollide(player, balls, False):
# The 'diff' lets you try to bounce the ball left or right
# depending where on the paddle you hit it
diff = (player.rect.x + player.width/2) - (ball.rect.x+ball.width/2)
# Set the ball's y position in case
# we hit the ball on the edge of the paddle
ball.rect.y = screen.get_height() - player.rect.height - ball.rect.height - 1
ball.bounce(diff)
你可以在每一帧上分别将每个东西画到屏幕上，但是告诉pygame为你做的更容易：
# Draw Everything
allsprites.draw(screen)
根据需要，事物可以在多个list中，例如将球添加到balls列表中，以便您可以轻松检查冲突，还可以添加到allsprites } list，以便您可以轻松地在屏幕上绘制所有内容
# Create the ball
ball = Ball()
allsprites.add(ball)
balls.add(ball)
修改：
一个重要的区别是allsprites实际上是sprite.Group。它里面有一个sprite列表，但它还有其他方法，如draw。
为了解决你的“什么是精灵”的问题，这只是一个在屏幕上绘制的东西。像sprite.Group.draw这样的pygame方法需要具有某些属性的事物列表 - 例如update。确保您使用正确名称提供所有这些属性的最简单方法是子类 Sprite，但这也是（强烈推荐）方便的事情 - 例如，这是来自pygame源代码：
虽然可以设计没有的精灵和组类 从下面的Sprite和AbstractGroup类派生，它是强烈的 建议您在添加Sprite或Group时扩展它们 类。
那么具体会对Sprite进行子类化吗？我们来看看源代码。以下是如何查找python模块的源代码：
>>> import pygame.sprite
>>> pygame.sprite.__file__
'c:\\Python27\\lib\\site-packages\\pygame\\sprite.py'
>>>
每个python模块都有一个__file__属性，可以告诉您源所在的位置（并非完全是每个）。如果在编辑器中打开它并向下滚动，则会看到Sprite的类定义：
class Sprite(object):
"""simple base class for visible game objects
pygame.sprite.Sprite(*groups): return Sprite
The base class for visible game objects. Derived classes will want to
override the Sprite.update() and assign a Sprite.image and
Sprite.rect attributes. The initializer can accept any number of
Group instances to be added to.
When subclassing the Sprite, be sure to call the base initializer before
adding the Sprite to Groups.
"""
def __init__(self, *groups):
self.__g = {} # The groups the sprite is in
if groups: self.add(groups)
def add(self, *groups):
"""add the sprite to groups
Sprite.add(*groups): return None
Any number of Group instances can be passed as arguments. The
Sprite will be added to the Groups it is not already a member of.
"""
has = self.__g.__contains__
for group in groups:
if hasattr(group, '_spritegroup'):
if not has(group):
group.add_internal(self)
self.add_internal(group)
else: self.add(*group)
def remove(self, *groups):
"""remove the sprite from groups
Sprite.remove(*groups): return None
Any number of Group instances can be passed as arguments. The Sprite will
be removed from the Groups it is currently a member of.
"""
has = self.__g.__contains__
for group in groups:
if hasattr(group, '_spritegroup'):
if has(group):
group.remove_internal(self)
self.remove_internal(group)
else: self.remove(*group)
def add_internal(self, group):
self.__g[group] = 0
def remove_internal(self, group):
del self.__g[group]
def update(self, *args):
"""method to control sprite behavior
Sprite.update(*args):
The default implementation of this method does nothing; it's just a
convenient "hook" that you can override. This method is called by
Group.update() with whatever arguments you give it.
There is no need to use this method if not using the convenience
method by the same name in the Group class.
"""
pass
def kill(self):
"""remove the Sprite from all Groups
Sprite.kill(): return None
The Sprite is removed from all the Groups that contain it. This won't
change anything about the state of the Sprite. It is possible to continue
to use the Sprite after this method has been called, including adding it
to Groups.
"""
for c in self.__g.keys():
c.remove_internal(self)
self.__g.clear()
def groups(self):
"""list of Groups that contain this Sprite
Sprite.groups(): return group_list
Return a list of all the Groups that contain this Sprite.
"""
return self.__g.keys()
def alive(self):
"""does the sprite belong to any groups
Sprite.alive(): return bool
Returns True when the Sprite belongs to one or more Groups.
"""
return (len(self.__g) != 0)
def __repr__(self):
return "<%s sprite(in %d groups)>" % (self.__class__.__name__, len(self.__g))
总而言之，你没有拥有来继承Sprite - 你可以自己提供所有这些方法 - 但如果你这样做会更容易;）