Pygame 贪吃蛇

目录

• 代码
• 遇到的问题
• 参考

代码

#-*-encoding=utf-8-*-
# Wormy(a Nibbles clone)
# By Al Sweigart al@inventwithpython.com
# http://inventwithpython.com/pygame
# Copied by Lei Song@1743207528@qq.com
import random,pygame,sys
from pygame.locals import *

FPS = 15
WINDOWWIDTH = 640
WINDOWHEIGHT = 480
CELLSIZE = 20 # 指一个单独的格子的尺寸
assert WINDOWWIDTH%CELLSIZE == 0,'Window width must be a multiple of cell size.' # 断言，窗口宽度必须是一个格子尺寸的整数倍
assert WINDOWHEIGHT%CELLSIZE == 0,'Window height must be a multiple of cell size.' # 断言，窗口高度必须是一个格子尺寸的整数倍
CELLWIDTH = int(WINDOWWIDTH /CELLSIZE)
CELLHEIGHT = int (WINDOWHEIGHT/CELLSIZE)

#          R G B
WHITE = (255,255,255)
BLACK = (0,0,0)
RED = (255,0,0)
GREEN = (0,255,0)
DARKGREEN = (0,155,0)
DARKGRAY = (40,40,40)
BGCOLOR = BLACK

UP = 'up'
DOWN = 'down'
LEFT = 'left'
RIGHT = 'right'

HEAD = 0 # syntactic sugar:index of the worm's head 语法糖，头部为0

def main():
    global FPSCLOCK,DISPLAYSURF,BASICFONT

    pygame.init() # 初始化
    FPSCLOCK = pygame.time.Clock()
    DISPLAYSURF = pygame.display.set_mode((WINDOWWIDTH,WINDOWHEIGHT))
    BASICFONT = pygame.font.Font('freesansbold.ttf',18)
    pygame.display.set_caption('Wormy')

    showStartScreen()
    while True:
        runGame()
        showGameOverScreen()


def runGame():
    # 确定一个随机的开始点
    startx = random.randint(5,CELLWIDTH - 6)
    starty = random.randint(5,CELLHEIGHT - 6)
    wormCoords = [{'x':startx,'y':starty},
                  {'x':startx-1,'y':starty},
                  {'x':startx-2,'y':starty}]#存储了身体，初始长度为3
    direction = RIGHT

    # 把苹果置于一个随机处
    apple = getRandomLocation()

    while True:# main game loop
        for event in pygame.event.get():# event handling loop
            if event.type==QUIT:
                terminate()
            elif event.type == KEYDOWN:# 按下键盘,wasd或者箭头
                if(event.key == K_LEFT or event.key == K_a)and direction != RIGHT:# 不能直接回头撞自己
                    direction = LEFT
                elif(event.key == K_RIGHT or event.key == K_d)and direction != LEFT:
                    direction = RIGHT
                elif(event.key == K_UP or event.key == K_w)and direction != DOWN:
                    direction = UP
                elif(event.key == K_DOWN or event.key == K_s)and direction != UP:
                    direction = DOWN
                elif event.key == K_ESCAPE:
                    terminate()

    # 检查它是否碰到自己或撞墙
        if wormCoords[HEAD]['x']==-1 or wormCoords[HEAD]['x']==CELLWIDTH or wormCoords[HEAD]['y']==-1 or wormCoords[HEAD]['y']==CELLHEIGHT:
            return# game over
        for wormBody in wormCoords[1:]:
            if wormBody['x']==wormCoords[HEAD]['x'] and wormBody['y']==wormCoords[HEAD]['y']:
                return# game over

    # 检查它是否恰到苹果
        if wormCoords[HEAD]['x']==apple['x'] and wormCoords[HEAD]['y']==apple['y']:
            apple = getRandomLocation()
        else:
            del wormCoords[-1]# 删除尾部

        # 如何做出移动的动画效果呢？方法是在蛇头前不断添加一个格子
        if direction == UP:
            newHead = {'x':wormCoords[HEAD]['x'],'y':wormCoords[HEAD]['y']-1}# 因为向下为正
        elif direction == DOWN:
            newHead = {'x':wormCoords[HEAD]['x'],'y':wormCoords[HEAD]['y']+1}
        elif direction == LEFT:
            newHead = {'x':wormCoords[HEAD]['x']-1,'y':wormCoords[HEAD]['y']}
        elif direction == RIGHT:
            newHead = {'x':wormCoords[HEAD]['x']+1,'y':wormCoords[HEAD]['y']}

        wormCoords.insert(0,newHead)# 加新头


        # 绘制屏幕Drawing the Screen
        DISPLAYSURF.fill(BGCOLOR)
        drawGrid()
        drawWorm(wormCoords)
        drawApple(apple)
        drawScore(len(wormCoords)-3)
        pygame.display.update()# 这一句draws the display Surface to the actual computer screen
        FPSCLOCK.tick(FPS/4)

# 绘制“Press a key”文本到屏幕上
def drawPressKeyMsg():
    pressKeySurf = BASICFONT.render('Press a key to play.',True,DARKGRAY)
    pressKeyRect = pressKeySurf.get_rect()
    pressKeyRect.topleft = (WINDOWWIDTH-200,WINDOWHEIGHT-30)
    DISPLAYSURF.blit(pressKeySurf,pressKeyRect)
#这个函数将被showStartScreen()和showGameOverScreen()两个函数调用

def checkForKeyPress():
    if len(pygame.event.get(QUIT))>0:# 返回一个列表，列表里是在事件队列中所有QUIT的事件，若无QUIT事件则返回空列表[]
        terminate()

    keyUpEvents = pygame.event.get(KEYUP)
    if len(keyUpEvents)==0:
        return None
    if keyUpEvents[0].key == K_ESCAPE:# 按了Esc键
        terminate()
    return keyUpEvents[0].key

# 开始屏幕
def showStartScreen():
    titleFont = pygame.font.Font('freesansbold.ttf',100)
    titleSurf1 = titleFont.render('Wormy!',True,WHITE,DARKGREEN)# 白字，墨绿背景
    titleSurf2 = titleFont.render('Wormy!',True,GREEN)# 绿字，透明背景

    degrees1 = 0
    degrees2 = 0
    while True:
        DISPLAYSURF.fill(BGCOLOR)
        rotatedSurf1 = pygame.transform.rotate(titleSurf1,degrees1)# 不会改变titleSurf1，而是返回一个新的Surface，上面画着旋转后的图像
        rotatedRect1 = rotatedSurf1.get_rect()
        rotatedRect1.center = (WINDOWWIDTH/2,WINDOWHEIGHT/2)
        DISPLAYSURF.blit(rotatedSurf1,rotatedRect1)
        # 新的矩形往往比原先的大。旋转的角度逆时针为正，顺时针为负。pygame会把你传的大于等于360°的度数不断减去360°直到其小于360°
        rotatedSurf2 = pygame.transform.rotate(titleSurf2,degrees2)
        rotatedRect2 = rotatedSurf2.get_rect()
        rotatedRect2.center = (WINDOWWIDTH/2,WINDOWHEIGHT/2)
        DISPLAYSURF.blit(rotatedSurf2,rotatedRect2)
        # 我们之所以不直接旋转rotatedSurf1和2是因为：1.旋转后的图形会失真，就像一张照片复印后再复印后不会与原来完全一样。不过如果旋转的角度为90°的倍数则不会出现这个问题。2.旋转后的矩形会变大，最终会超出pygame的承受范围
        drawPressKeyMsg()

        if checkForKeyPress():
            pygame.event.get()# 清空事件队列
            return
        pygame.display.update()
        FPSCLOCK.tick(FPS)
        degrees1 += 3# 每帧转3°
        degrees2 += 7# 每帧转7°


def terminate():
    pygame.quit()
    sys.exit()


def getRandomLocation():
    return {'x':random.randint(0,CELLWIDTH-1),'y':random.randint(0,CELLHEIGHT - 1)}
    # 决定苹果出现的位置

def showGameOverScreen():
    gameOverFont = pygame.font.Font('freesansbold.ttf',150)
    gameSurf = gameOverFont.render('Game',True,WHITE)
    overSurf = gameOverFont.render('Over',True,WHITE)
    gameRect = gameSurf.get_rect()
    overRect = overSurf.get_rect()
    gameRect.midtop = (WINDOWWIDTH/2,10)
    overRect.midtop = (WINDOWWIDTH/2,gameRect.height+10+25)

    DISPLAYSURF.blit(gameSurf,gameRect)
    DISPLAYSURF.blit(overSurf,overRect)
    drawPressKeyMsg()
    pygame.display.update()
    pygame.time.wait(500)# 500毫秒，也就是半秒
    checkForKeyPress()# 清空事件队列中的任何按键

    while True:
        if checkForKeyPress():
            pygame.event.get()# 清空事件队列
            return

def drawScore(score):
    scoreSurf = BASICFONT.render('Score:%s'%(score),True,WHITE)
    scoreRect = scoreSurf.get_rect()
    scoreRect.topleft = (WINDOWWIDTH-120,10)
    DISPLAYSURF.blit(scoreSurf,scoreRect)


def drawWorm(wormCoords):
    for coord in wormCoords:
        x = coord['x']*CELLSIZE
        y = coord['y']*CELLSIZE
        wormSegmentRect = pygame.Rect(x,y,CELLSIZE,CELLSIZE)
        pygame.draw.rect(DISPLAYSURF,DARKGREEN,wormSegmentRect)
        wormInnerSegmentRect = pygame.Rect(x+4,y+4,CELLSIZE-8,CELLSIZE-8)
        pygame.draw.rect(DISPLAYSURF,GREEN,wormInnerSegmentRect)


def drawApple(coord):
    x = coord['x']*CELLSIZE
    y = coord['y']*CELLSIZE
    appleRect = pygame.Rect(x,y,CELLSIZE,CELLSIZE)
    pygame.draw.rect(DISPLAYSURF,RED,appleRect)


def drawGrid():
    for x in range(0,WINDOWWIDTH,CELLSIZE):# draw vertical lines
        pygame.draw.line(DISPLAYSURF,DARKGRAY,(x,0),(x,WINDOWHEIGHT))
    for y in range(0,WINDOWHEIGHT,CELLSIZE):# draw horizontal lines
        pygame.draw.line(DISPLAYSURF,DARKGRAY,(0,y),(WINDOWWIDTH,y))


if __name__=='__main__':
    main()

遇到的问题

在参考的源代码中，有下面这样一段（apple打错了，打成了apply）：

            # check if worm has eaten an apply
        if wormCoords[HEAD]['x'] == apple['x'] and wormCoords[HEAD]['y'] == apple['y']:
            # don't remove worm's tail segment
            apple = getRandomLocation() # set a new apple somewhere
        else:
             del wormCoords[-1] # remove worm's tail segment

        # move the worm by adding a segment in the direction it is moving
        if direction == UP:
            newHead = {'x': wormCoords[HEAD]['x'], 'y': wormCoords[HEAD]['y'] - 1}
        elif direction == DOWN:
            newHead = {'x': wormCoords[HEAD]['x'], 'y': wormCoords[HEAD]['y'] + 1}
        elif direction == LEFT:
            newHead = {'x': wormCoords[HEAD]['x'] - 1, 'y': wormCoords[HEAD]['y']}
        elif direction == RIGHT:
            newHead = {'x': wormCoords[HEAD]['x'] + 1, 'y': wormCoords[HEAD]['y']}
        wormCoords.insert(0, newHead)

这段代码的第一个 if-else 意思是，如果蛇恰到了苹果，就重新生成一个苹果的位置，否则删去蛇尾的一个方块。下面的四句 if 和 elif 则是根据蛇运动的不同方向为蛇添加一个新的头部方块。
我一想，这不是多余了吗？为什么每次都要添加头部，在吃不到苹果的时候才删除尾部呢，直接在吃到苹果的时候添加头部不就简单了吗？于是下面是我一开始写的代码：

        # 检查它是否恰到苹果
        if wormCoords[HEAD]['x']==apple['x'] and wormCoords[HEAD]['y']==apple['y']:
            apple = getRandomLocation()
            if direction == UP:
                newHead = {'x':wormCoords[HEAD]['x'],'y':wormCoords[HEAD]['y']-1}# 因为向下为正
            elif direction == DOWN:
                newHead = {'x':wormCoords[HEAD]['x'],'y':wormCoords[HEAD]['y']+1}
            elif direction == LEFT:
                newHead = {'x':wormCoords[HEAD]['x']-1,'y':wormCoords[HEAD]['y']}
            elif direction == RIGHT:
                newHead = {'x':wormCoords[HEAD]['x']+1,'y':wormCoords[HEAD]['y']}
            wormCoords.insert(0,newHead)# 加新头

没想到，运行后开始游戏后蛇完全不动弹！成了一张静止的图片！这是为什么呢？

于是我开始思考，那么蛇到底是怎么移动起来的呢？原来，答案就在上面这段源代码中。蛇“移动”的方式是不断向蛇头添加小块同时删除尾部小块，在吃到苹果时才不删除尾部，这样就能做出“移动”的效果啦。

参考

inventwithpython