利用Python如何制作贪吃蛇及AI版贪吃蛇详解

import random
import pygame
import sys
from pygame.locals import *
 
snakespeed = 17
window_width = 800
window_height = 500
cell_size = 20 # width and height of the cells
# ensuring that the cells fit perfectly in the window. eg if cell size was
# 10 and window width or windowheight were 15 only 1.5 cells would
# fit.
assert window_width % cell_size == 0, "window width must be a multiple of cell size."
# ensuring that only whole integer number of cells fit perfectly in the window.
assert window_height % cell_size == 0, "window height must be a multiple of cell size."
cell_w = int(window_width / cell_size) # cell width
cell_h = int(window_height / cell_size) # cellc height
 
 
white = (255, 255, 255)
black = (0, 0, 0)
red = (255, 0, 0) # defining element colors for the program.
green = (0, 255, 0)
darkgreen = (0, 155, 0)
darkgray = (40, 40, 40)
yellow = (255, 255, 0)
red_dark = (150, 0, 0)
blue = (0, 0, 255)
blue_dark = (0, 0, 150)
 
 
bgcolor = black # background color
 
 
up = 'up'
down = 'down' # defining keyboard keys.
left = 'left'
right = 'right'
 
head = 0 # syntactic sugar: index of the snake's head
 
 
def main():
 global snakespeedclock, displaysurf, basicfont
 
 pygame.init()
 snakespeedclock = pygame.time.clock()
 displaysurf = pygame.display.set_mode((window_width, window_height))
 basicfont = pygame.font.font('freesansbold.ttf', 18)
 pygame.display.set_caption('snake')
 
 showstartscreen()
 while true:
 rungame()
 showgameoverscreen()
 
 
def rungame():
 # set a random start point.
 startx = random.randint(5, cell_w - 6)
 starty = random.randint(5, cell_h - 6)
 wormcoords = [{'x': startx, 'y': starty},
   {'x': startx - 1, 'y': starty},
   {'x': startx - 2, 'y': starty}]
 direction = right
 
 # start the apple in a random place.
 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:
  if (event.key == k_left) and direction != right:
   direction = left
  elif (event.key == k_right) and direction != left:
   direction = right
  elif (event.key == k_up) and direction != down:
   direction = up
  elif (event.key == k_down) and direction != up:
   direction = down
  elif event.key == k_escape:
   terminate()
 
 # check if the snake has hit itself or the edge
 if wormcoords[head]['x'] == -1 or wormcoords[head]['x'] == cell_w or wormcoords[head]['y'] == -1 or wormcoords[head]['y'] == cell_h:
  return # game over
 for wormbody in wormcoords[1:]:
  if wormbody['x'] == wormcoords[head]['x'] and wormbody['y'] == wormcoords[head]['y']:
  return # game over
 
 # check if snake 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)
 displaysurf.fill(bgcolor)
 drawgrid()
 drawworm(wormcoords)
 drawapple(apple)
 drawscore(len(wormcoords) - 3)
 pygame.display.update()
 snakespeedclock.tick(snakespeed)
 
 
def drawpresskeymsg():
 presskeysurf = basicfont.render('press a key to play.', true, white)
 presskeyrect = presskeysurf.get_rect()
 presskeyrect.topleft = (window_width - 200, window_height - 30)
 displaysurf.blit(presskeysurf, presskeyrect)
 
 
def checkforkeypress():
 if len(pygame.event.get(quit)) > 0:
 terminate()
 keyupevents = pygame.event.get(keyup)
 if len(keyupevents) == 0:
 return none
 if keyupevents[0].key == k_escape:
 terminate()
 return keyupevents[0].key
 
 
def showstartscreen():
 titlefont = pygame.font.font('freesansbold.ttf', 100)
 titlesurf1 = titlefont.render('snake!', true, white, darkgreen)
 degrees1 = 0
 degrees2 = 0
 while true:
 displaysurf.fill(bgcolor)
 rotatedsurf1 = pygame.transform.rotate(titlesurf1, degrees1)
 rotatedrect1 = rotatedsurf1.get_rect()
 rotatedrect1.center = (window_width / 2, window_height / 2)
 displaysurf.blit(rotatedsurf1, rotatedrect1)
 
 drawpresskeymsg()
 
 if checkforkeypress():
  pygame.event.get() # clear event queue
  return
 pygame.display.update()
 snakespeedclock.tick(snakespeed)
 degrees1 += 3 # rotate by 3 degrees each frame
 degrees2 += 7 # rotate by 7 degrees each frame
 
 
def terminate():
 pygame.quit()
 sys.exit()
 
 
def getrandomlocation():
 return {'x': random.randint(0, cell_w - 1), 'y': random.randint(0, cell_h - 1)}
 
 
def showgameoverscreen():
 gameoverfont = pygame.font.font('freesansbold.ttf', 100)
 gamesurf = gameoverfont.render('game', true, white)
 oversurf = gameoverfont.render('over', true, white)
 gamerect = gamesurf.get_rect()
 overrect = oversurf.get_rect()
 gamerect.midtop = (window_width / 2, 10)
 overrect.midtop = (window_width / 2, gamerect.height + 10 + 25)
 
 displaysurf.blit(gamesurf, gamerect)
 displaysurf.blit(oversurf, overrect)
 drawpresskeymsg()
 pygame.display.update()
 pygame.time.wait(500)
 checkforkeypress() # clear out any key presses in the event queue
 
 while true:
 if checkforkeypress():
  pygame.event.get() # clear event queue
  return
 
 
def drawscore(score):
 scoresurf = basicfont.render('score: %s' % (score), true, white)
 scorerect = scoresurf.get_rect()
 scorerect.topleft = (window_width - 120, 10)
 displaysurf.blit(scoresurf, scorerect)
 
 
def drawworm(wormcoords):
 for coord in wormcoords:
 x = coord['x'] * cell_size
 y = coord['y'] * cell_size
 wormsegmentrect = pygame.rect(x, y, cell_size, cell_size)
 pygame.draw.rect(displaysurf, darkgreen, wormsegmentrect)
 worminnersegmentrect = pygame.rect(
  x + 4, y + 4, cell_size - 8, cell_size - 8)
 pygame.draw.rect(displaysurf, green, worminnersegmentrect)
 
 
def drawapple(coord):
 x = coord['x'] * cell_size
 y = coord['y'] * cell_size
 applerect = pygame.rect(x, y, cell_size, cell_size)
 pygame.draw.rect(displaysurf, red, applerect)
 
 
def drawgrid():
 for x in range(0, window_width, cell_size): # draw vertical lines
 pygame.draw.line(displaysurf, darkgray, (x, 0), (x, window_height))
 for y in range(0, window_height, cell_size): # draw horizontal lines
 pygame.draw.line(displaysurf, darkgray, (0, y), (window_width, y))
 
 
if __name__ == '__main__':
 try:
 main()
 except systemexit:
 pass

#coding: utf-8
import pygame,sys,time,random
from pygame.locals import *
# 定义颜色变量
redcolour = pygame.color(255,0,0)
blackcolour = pygame.color(0,0,0)
whitecolour = pygame.color(255,255,255)
greencolour = pygame.color(0,255,0)
headcolour = pygame.color(0,119,255)

#注意：在下面所有的除法中，为了防止pygame输出偏差，必须取除数(//)而不是单纯除法(/)

# 蛇运动的场地长宽，因为第0行，height行，第0列，width列为围墙，所以实际是13*13
height = 15
width = 15
field_size = height * width
# 蛇头位于snake数组的第一个元素
head = 0

# 用数字代表不同的对象，由于运动时矩阵上每个格子会处理成到达食物的路径长度，
# 因此这三个变量间需要有足够大的间隔(>height*width)来互相区分
# 小写一般是坐标，大写代表常量
food = 0
undefined = (height + 1) * (width + 1)
snake = 2 * undefined

# 由于snake是一维数组，所以对应元素直接加上以下值就表示向四个方向移动
left = -1
right = 1
up = -width#一维数组，所以需要整个宽度都加上才能表示上下移动
down = width 

# 错误码
err = -2333

# 用一维数组来表示二维的东西
# board表示蛇运动的矩形场地
# 初始化蛇头在(1,1)的地方
# 初始蛇长度为1
board = [0] * field_size #[0,0,0,……]
snake = [0] * (field_size+1)
snake[head] = 1*width+1
snake_size = 1
# 与上面变量对应的临时变量，蛇试探性地移动时使用
tmpboard = [0] * field_size
tmpsnake = [0] * (field_size+1)
tmpsnake[head] = 1*width+1
tmpsnake_size = 1

# food:食物位置初始在(4, 7)
# best_move: 运动方向
food = 4 * width + 7
best_move = err

# 运动方向数组，游戏分数(蛇长)
mov = [left, right, up, down]           
score = 1 

# 检查一个cell有没有被蛇身覆盖，没有覆盖则为free，返回true
def is_cell_free(idx, psize, psnake):
 return not (idx in psnake[:psize]) 

# 检查某个位置idx是否可向move方向运动
def is_move_possible(idx, move):
 flag = false
 if move == left:
  #因为实际范围是13*13,[1,13]*[1,13],所以idx为1时不能往左跑，此时取余为1所以>1
  flag = true if idx%width > 1 else false
 elif move == right:
  #这里的<width-2跟上面是一样的道理
  flag = true if idx%width < (width-2) else false
 elif move == up:
  #这里向上的判断画图很好理解，因为在[1,13]*[1,13]的实际运动范围外，还有个
  #大框是围墙，就是之前说的那几个行列，下面判断向下运动的条件也是类似的
  flag = true if idx > (2*width-1) else false
 elif move == down:
  flag = true if idx < (field_size-2*width) else false
 return flag
# 重置board
# board_bfs后，undefined值都变为了到达食物的路径长度
# 如需要还原，则要重置它
def board_reset(psnake, psize, pboard):
 for i in range(field_size):
  if i == food:
   pboard[i] = food
  elif is_cell_free(i, psize, psnake): # 该位置为空
   pboard[i] = undefined
  else: # 该位置为蛇身
   pboard[i] = snake
 
# 广度优先搜索遍历整个board，
# 计算出board中每个非snake元素到达食物的路径长度
def board_bfs(pfood, psnake, pboard):
 queue = []
 queue.append(pfood)
 inqueue = [0] * field_size
 found = false
 # while循环结束后，除了蛇的身体，
 # 其它每个方格中的数字为从它到食物的曼哈顿间距
 while len(queue)!=0: 
  idx = queue.pop(0)#初始时idx是食物的坐标 
  if inqueue[idx] == 1: continue
  inqueue[idx] = 1
  for i in range(4):#左右上下
   if is_move_possible(idx, mov[i]):
    if idx + mov[i] == psnake[head]:
     found = true
    if pboard[idx+mov[i]] < snake: # 如果该点不是蛇的身体
     if pboard[idx+mov[i]] > pboard[idx]+1:#小于的时候不管，不然会覆盖已有的路径数据
      pboard[idx+mov[i]] = pboard[idx] + 1
     if inqueue[idx+mov[i]] == 0:
      queue.append(idx+mov[i])
 return found

# 从蛇头开始，根据board中元素值，
# 从蛇头周围4个领域点中选择最短路径
def choose_shortest_safe_move(psnake, pboard):
 best_move = err
 min = snake
 for i in range(4):
  if is_move_possible(psnake[head], mov[i]) and pboard[psnake[head]+mov[i]]<min:
   #这里判断最小和下面的函数判断最大，都是先赋值，再循环互相比较
   min = pboard[psnake[head]+mov[i]]
   best_move = mov[i]
 return best_move

# 从蛇头开始，根据board中元素值，
# 从蛇头周围4个领域点中选择最远路径
def choose_longest_safe_move(psnake, pboard):
 best_move = err
 max = -1
 for i in range(4):
  if is_move_possible(psnake[head], mov[i]) and pboard[psnake[head]+mov[i]]<undefined and pboard[psnake[head]+mov[i]]>max:
   max = pboard[psnake[head]+mov[i]]
   best_move = mov[i]
 return best_move

# 检查是否可以追着蛇尾运动，即蛇头和蛇尾间是有路径的
# 为的是避免蛇头陷入死路
# 虚拟操作，在tmpboard,tmpsnake中进行
def is_tail_inside():
 global tmpboard, tmpsnake, food, tmpsnake_size
 tmpboard[tmpsnake[tmpsnake_size-1]] = 0 # 虚拟地将蛇尾变为食物(因为是虚拟的，所以在tmpsnake,tmpboard中进行)
 tmpboard[food] = snake # 放置食物的地方，看成蛇身
 result = board_bfs(tmpsnake[tmpsnake_size-1], tmpsnake, tmpboard) # 求得每个位置到蛇尾的路径长度
 for i in range(4): # 如果蛇头和蛇尾紧挨着，则返回false。即不能follow_tail，追着蛇尾运动了
  if is_move_possible(tmpsnake[head], mov[i]) and tmpsnake[head]+mov[i]==tmpsnake[tmpsnake_size-1] and tmpsnake_size>3:
   result = false
 return result

# 让蛇头朝着蛇尾运行一步
# 不管蛇身阻挡，朝蛇尾方向运行
def follow_tail():
 global tmpboard, tmpsnake, food, tmpsnake_size
 tmpsnake_size = snake_size
 tmpsnake = snake[:]
 board_reset(tmpsnake, tmpsnake_size, tmpboard) # 重置虚拟board
 tmpboard[tmpsnake[tmpsnake_size-1]] = food # 让蛇尾成为食物
 tmpboard[food] = snake # 让食物的地方变成蛇身
 board_bfs(tmpsnake[tmpsnake_size-1], tmpsnake, tmpboard) # 求得各个位置到达蛇尾的路径长度
 tmpboard[tmpsnake[tmpsnake_size-1]] = snake # 还原蛇尾
 return choose_longest_safe_move(tmpsnake, tmpboard) # 返回运行方向(让蛇头运动1步)

# 在各种方案都不行时，随便找一个可行的方向来走(1步),
def any_possible_move():
 global food , snake, snake_size, board
 best_move = err
 board_reset(snake, snake_size, board)
 board_bfs(food, snake, board)
 min = snake

 for i in range(4):
  if is_move_possible(snake[head], mov[i]) and board[snake[head]+mov[i]]<min:
   min = board[snake[head]+mov[i]]
   best_move = mov[i]
 return best_move
 
#转换数组函数
def shift_array(arr, size):
 for i in range(size, 0, -1):
  arr[i] = arr[i-1]

def new_food():#随机函数生成新的食物
 global food, snake_size
 cell_free = false
 while not cell_free:
  w = random.randint(1, width-2)
  h = random.randint(1, height-2)
  food = width*h + w
  cell_free = is_cell_free(food, snake_size, snake)
 pygame.draw.rect(playsurface,redcolour,rect(18*(food//width), 18*(food%width),18,18))

# 真正的蛇在这个函数中，朝pbest_move走1步
def make_move(pbest_move):
 global snake, board, snake_size, score
 shift_array(snake, snake_size)
 snake[head] += pbest_move
 p = snake[head]
 for body in snake:#画蛇，身体，头，尾
  pygame.draw.rect(playsurface,whitecolour,rect(18*(body//width), 18*(body%width),18,18))
 pygame.draw.rect(playsurface,greencolour,rect(18*(snake[snake_size-1]//width),18*(snake[snake_size-1]%width),18,18))
 pygame.draw.rect(playsurface,headcolour,rect(18*(p//width), 18*(p%width),18,18))
 #下面一行是把初始情况会出现的第一个白块bug填掉
 pygame.draw.rect(playsurface,(255,255,0),rect(0,0,18,18))
 # 刷新pygame显示层
 pygame.display.flip() 
 
 # 如果新加入的蛇头就是食物的位置
 # 蛇长加1，产生新的食物，重置board(因为原来那些路径长度已经用不上了)
 if snake[head] == food:
  board[snake[head]] = snake # 新的蛇头
  snake_size += 1
  score += 1
  if snake_size < field_size: new_food()
 else: # 如果新加入的蛇头不是食物的位置
  board[snake[head]] = snake # 新的蛇头
  board[snake[snake_size]] = undefined # 蛇尾变为undefined，黑色
  pygame.draw.rect(playsurface,blackcolour,rect(18*(snake[snake_size]//width),18*(snake[snake_size]%width),18,18))
  # 刷新pygame显示层
  pygame.display.flip() 

# 虚拟地运行一次，然后在调用处检查这次运行可否可行
# 可行才真实运行。
# 虚拟运行吃到食物后，得到虚拟下蛇在board的位置
def virtual_shortest_move():
 global snake, board, snake_size, tmpsnake, tmpboard, tmpsnake_size, food
 tmpsnake_size = snake_size
 tmpsnake = snake[:] # 如果直接tmpsnake=snake，则两者指向同一处内存
 tmpboard = board[:] # board中已经是各位置到达食物的路径长度了，不用再计算
 board_reset(tmpsnake, tmpsnake_size, tmpboard)
 
 food_eated = false
 while not food_eated:
  board_bfs(food, tmpsnake, tmpboard) 
  move = choose_shortest_safe_move(tmpsnake, tmpboard)
  shift_array(tmpsnake, tmpsnake_size)
  tmpsnake[head] += move # 在蛇头前加入一个新的位置
  # 如果新加入的蛇头的位置正好是食物的位置
  # 则长度加1，重置board，食物那个位置变为蛇的一部分(snake)
  if tmpsnake[head] == food:
   tmpsnake_size += 1
   board_reset(tmpsnake, tmpsnake_size, tmpboard) # 虚拟运行后，蛇在board的位置
   tmpboard[food] = snake
   food_eated = true
  else: # 如果蛇头不是食物的位置，则新加入的位置为蛇头，最后一个变为空格
   tmpboard[tmpsnake[head]] = snake
   tmpboard[tmpsnake[tmpsnake_size]] = undefined

# 如果蛇与食物间有路径，则调用本函数
def find_safe_way():
 global snake, board
 safe_move = err
 # 虚拟地运行一次，因为已经确保蛇与食物间有路径，所以执行有效
 # 运行后得到虚拟下蛇在board中的位置，即tmpboard
 virtual_shortest_move() # 该函数唯一调用处
 if is_tail_inside(): # 如果虚拟运行后，蛇头蛇尾间有通路，则选最短路运行(1步)
  return choose_shortest_safe_move(snake, board)
 safe_move = follow_tail() # 否则虚拟地follow_tail 1步，如果可以做到，返回true
 return safe_move


#初始化pygame
pygame.init()
#定义一个变量用来控制游戏速度
fpsclock = pygame.time.clock()
# 创建pygame显示层
playsurface = pygame.display.set_mode((270,270))
pygame.display.set_caption('贪吃蛇')
# 绘制pygame显示层
playsurface.fill(blackcolour)
#初始化食物
pygame.draw.rect(playsurface,redcolour,rect(18*(food//width), 18*(food%width),18,18))

while true:
 for event in pygame.event.get():#循环监听键盘和退出事件
  if event.type == quit:#如果点了关闭
   print(score)#游戏结束后打印分数
   pygame.quit()
   sys.exit()
  elif event.type == keydown:#如果esc键被按下
   if event.key==k_escape:
    print(score)#游戏结束后打印分数
    pygame.quit()
    sys.exit()
 # 刷新pygame显示层
 pygame.display.flip() 
 #画围墙，255,255,0是黄色，边框是36是因为，pygame矩形是以边为初始，向四周填充边框
 pygame.draw.rect(playsurface,(255,255,0),rect(0,0,270,270),36)
 # 重置距离
 board_reset(snake, snake_size, board)
 # 如果蛇可以吃到食物，board_bfs返回true
 # 并且board中除了蛇身(=snake)，其它的元素值表示从该点运动到食物的最短路径长
 if board_bfs(food, snake, board):
  best_move = find_safe_way() # find_safe_way的唯一调用处
 else:
  best_move = follow_tail()
 if best_move == err:
  best_move = any_possible_move()
 # 上面一次思考，只得出一个方向，运行一步
 if best_move != err: make_move(best_move)
 else:
  print(score)#游戏结束后打印分数
  break
 # 控制游戏速度
 fpsclock.tick(20)#20看上去速度正好