好的,我正在使用inventwith
python来教我自己如何编码.我试图以我自己的方式重用代码来理解它是如何工作的,但这部分给了我麻烦：

在Chapter 17中有一组动画代码,其中不同大小的框从屏幕侧面反弹

for b in blocks:
    # move the block data structure
    if b['dir'] == DOWNLEFT:
        b['rect'].left -= MOVESPEED
        b['rect'].top += MOVESPEED
    if b['dir'] == DOWNRIGHT:
        b['rect'].left += MOVESPEED
        b['rect'].top += MOVESPEED
    if b['dir'] == UPLEFT:
        b['rect'].left -= MOVESPEED
        b['rect'].top -= MOVESPEED
    if b['dir'] == UPRIGHT:
        b['rect'].left += MOVESPEED
        b['rect'].top -= MOVESPEED

    # check if the block has move out of the window
    if b['rect'].top < 0:
        # block has moved past the top
        if b['dir'] == UPLEFT:
            b['dir'] = DOWNLEFT
        if b['dir'] == UPRIGHT:
            b['dir'] = DOWNRIGHT
    if b['rect'].bottom > WINDOWHEIGHT:
        # block has moved past the bottom
        if b['dir'] == DOWNLEFT:
            b['dir'] = UPLEFT
        if b['dir'] == DOWNRIGHT:
            b['dir'] = UPRIGHT
    if b['rect'].left < 0:
        # block has moved past the left side
        if b['dir'] == DOWNLEFT:
            b['dir'] = DOWNRIGHT
        if b['dir'] == UPLEFT:
            b['dir'] = UPRIGHT
    if b['rect'].right > WINDOWWIDTH:
        # block has moved past the right side
        if b['dir'] == DOWNRIGHT:
            b['dir'] = DOWNLEFT
        if b['dir'] == UPRIGHT:
            b['dir'] = UPLEFT

我想创建它,以便我的块左右移动并从屏幕的每一侧反弹.

但是,当我尝试自己更改此代码时,所有发生的事情都是块在屏幕上飞出而没有弹跳.尝试了几种变体,结果完全相同.目前它看起来像这样：
编辑：更新完整代码

import pygame, sys, time
from pygame.locals import *

# set up pygame
pygame.init()

# set up the window
WINDOWWIDTH = 480
WINDOWHEIGHT = 800
windowSurface = pygame.display.set_mode((WINDOWWIDTH, WINDOWHEIGHT), 0, 32)
pygame.display.set_caption('Jumper')

#Directions
LEFT = 4
RIGHT = 6
UP = 8
DOWN = 2

MOVESPEED = 4

# set up the colors
BLACK = (0, 0, 0)
RED = (255, 0, 0)
GREEN = (0, 255, 0)
BLUE = (0, 0, 255)


b1 = {'rect':pygame.Rect(240, 700, 20, 20), 'color':GREEN, 'dir':LEFT}
blocks = [b1]

# run the game loop
while True:
# check for the QUIT event
for event in pygame.event.get():
    if event.type == QUIT:
        pygame.quit()
        sys.exit()

# draw the black background onto the surface
windowSurface.fill(BLACK)

for b in blocks:
    # move the block data structure
    if b['dir'] == LEFT:
        b['rect'].left -= MOVESPEED
    if b['dir'] == RIGHT:
        b['rect'].left += MOVESPEED

        if b['rect'].left < 0:
             b['dir'] = RIGHT


        if b['rect'].right > WINDOWWIDTH:
                b['dir'] = LEFT

             # draw the block onto the surface
    pygame.draw.rect(windowSurface, b['color'], b['rect'])

# draw the window onto the screen
pygame.display.update()
time.sleep(0.02)

最佳答案 代码中的问题只是混合缩进.如果您修复了缩进,它可以正常工作：

import pygame, sys, time
from pygame.locals import *

# set up pygame
pygame.init()

# set up the window
WINDOWWIDTH = 480
WINDOWHEIGHT = 800
windowSurface = pygame.display.set_mode((WINDOWWIDTH, WINDOWHEIGHT), 0, 32)
pygame.display.set_caption('Jumper')

#Directions
LEFT = 4
RIGHT = 6
UP = 8
DOWN = 2

MOVESPEED = 4

# set up the colors
BLACK = (0, 0, 0)
RED = (255, 0, 0)
GREEN = (0, 255, 0)
BLUE = (0, 0, 255)


b1 = {'rect':pygame.Rect(240, 700, 20, 20), 'color':GREEN, 'dir':LEFT}
blocks = [b1]

# run the game loop
while True:
    # check for the QUIT event
    for event in pygame.event.get():
        if event.type == QUIT:
            pygame.quit()
            sys.exit()

    # draw the black background onto the surface
    windowSurface.fill(BLACK)

    for b in blocks:
        # move the block data structure
        if b['dir'] == LEFT:
            b['rect'].left -= MOVESPEED
        if b['dir'] == RIGHT:
            b['rect'].left += MOVESPEED

        if b['rect'].left < 0:
             b['dir'] = RIGHT
        if b['rect'].right > WINDOWWIDTH:
                b['dir'] = LEFT

        # draw the block onto the surface
        pygame.draw.rect(windowSurface, b['color'], b['rect'])

    # draw the window onto the screen
    pygame.display.update()

time.sleep(0.02)

Python使用缩进来告诉嵌套内容是什么.在C#和其他使用花括号或其他块分隔符的语言中,只要将花括号放在正确的位置,就可以使用错误的缩进.但在Python中,缩进很重要. (在所有其他语言中,正确的缩进对于代码可读性仍然至关重要,即使编译器不关心它.)

将您的代码版本与上面的代码进行比较,您将看到需要修复缩进的位置.

现在谈到一个更大的问题.来自Inventing With Python网站的示例代码是……说得好,不太好.

假装您对编程一无所知,只需看看您开始使用的原始代码.难道看起来那里有大量的重复吗？

那非常棘手的重复.看看它设法使用DOWNLEFT,DOWNRIGHT,UPLEFT,UPRIGHT的所有不同方式,以及代码必须如此小心,以便每次都能正确使用.

每当你想要编写这种棘手的代码时,请停下来,坐下来问问自己,“难道不是有更简单的方法吗？”

事实上,你肯定是在正确的轨道上删除一堆复杂的代码,并为你的实验做一些简单的事情.

但只是为了好玩,让我们回到他们的代码,看看我们如何简化它,但仍然做它所做的一切.

从这四个名字开始,DOWNLEFT等.为什么每个人都有自己的名字？他们真的都不是基本相同吗？它们都是对角线,只是不同方向的对角线.

正如名字所暗示的那样,对角线实际上是两个方向的组合,纵向和横向.

现在,我们如何在屏幕/窗口上指定位置？我们没有为每个可能的位置命名,我们给它一个x和y值的坐标.最左边的最顶部像素是x = 0,y = 0,我们从那里开始,向右或向下添加一个,向左或向上减去一个.

因此,不要为四个对角线方向编制名称,而是使用实际数字！我们将表示DOWNRIGHT为x = 1,y = 1,UPLEFT表示为x = -1,y = -1等.

现在发生了一件美妙的事情考虑检查左边缘反弹的代码(如果b [‘rect’].左< 0).我们可以忽略y方向,只需将x = -1更改为x = 1,而不必使特殊情况将DOWNLEFT更改为DOWNRIGHT或UPLEFT更改为UPRIGHT. 除了我们将x = 1更改为x = -1之外,从右边缘反弹也是如此.事实上,你可以通过将x乘以-1来处理这两种情况. 所以我们可以做到这一点：如果我们碰到左边或右边,我们将x方向乘以-1.对于顶部或底部边缘和y方向也是如此. 以下是执行此操作的原始代码的修订版,并进行了一些其他简化：

import pygame, sys, time
from pygame.locals import *

class Block( object ):
    def __init__( self, rect, color, dir ):
        self.rect = rect
        self.color = color
        self.dir = dir
    def move( self ):
        # reverse direction if the block will move out of the window
        if self.rect.left < SPEED or self.rect.right > WIN_WIDTH - SPEED:
            self.dir.x *= -1
        if self.rect.top < SPEED or self.rect.bottom > WIN_HEIGHT - SPEED:
            self.dir.y *= -1
        # move the block
        self.rect.left += self.dir.x * SPEED
        self.rect.top += self.dir.y * SPEED
    def draw( self ):
        pygame.draw.rect( windowSurface, self.color, self.rect )

class Direction( object ):
    def __init__( self, x, y ):
        self.x = x
        self.y = y

# set up pygame
pygame.init()

# set up the window
WIN_WIDTH = 400
WIN_HEIGHT = 400
windowSurface = pygame.display.set_mode( ( WIN_WIDTH, WIN_HEIGHT ), 0, 32 )
pygame.display.set_caption( 'Animation' )

# set up the movement speed
SPEED = 4

# set up the colors
BLACK = ( 0, 0, 0 )
RED = ( 255, 0, 0 )
GREEN = ( 0, 255, 0 )
BLUE = ( 0, 0, 255 )

# set up the block objects
blocks = [
    Block( pygame.Rect( 300, 80, 50, 100 ), RED, Direction( -1, 1 ) ),
    Block( pygame.Rect( 200, 200, 20, 20 ), GREEN, Direction( -1, -1 ) ),
    Block( pygame.Rect( 100, 150, 60, 60 ), BLUE, Direction( 1, -1 ) ),
]

# run the game loop
while True:
    # check for the QUIT event
    for event in pygame.event.get():
        if event.type == QUIT:
            pygame.quit()
            sys.exit()

    # draw the black background onto the surface
    windowSurface.fill( BLACK )

    # move and draw each block
    for block in blocks:
        block.move()
        block.draw()

    # draw the window onto the screen
    pygame.display.update()
    time.sleep( 0.02 )

我还为块和方向创建了类,而不是使用内联代码完成所有操作.注意主要的“移动和绘制”循环现在只是三行代码,而不是原始代码中的巨大复杂混乱.

您应该从C#背景中熟悉类. Python中的符号略有不同 – 例如,__ init __()是构造函数 – 但概念非常相似.如果代码中的任何内容不清楚,请告诉我.

还有一个小错误修复：原始代码让块在反转之前经过屏幕边缘,因此我在边缘测试越过边缘之前调整边缘测试.这就是为什么它说,例如,如果self.rect.left< SPEED而不是self.rect.left< 0.