python 井字棋（Tic Tac Toe）

说明

用python实现了井字棋，整个框架是本人自己构思的，自认为比较满意。另外，90%+的代码也是本人逐字逐句敲的。

minimax算法还没完全理解，所以参考了这里的代码，并作了修改。

特点

可以选择人人、人机、机人、机机四种对战模式之一

电脑玩家的AI使用了minimax算法，带apha-beta剪枝

电脑玩家在思考时，时时刻刻都有一个“假想敌”。以便使得minimax算法运转起来

代码

作者：hhh5460
时间：2017年6月26日

# 棋盘
class Board(object):
def __init__(self):
#self._board = '-'*9 # 坑！！
self._board = ['-' for _ in range(9)]
self._history = [] # 棋谱

# 按指定动作，放入棋子
def _move(self, action, take):
if self._board[action] == '-':
self._board[action] = take

self._history.append((action, take)) # 加入棋谱

# 撤销动作，拿走棋子
def _unmove(self, action):
self._board[action] = '-'

self._history.pop()

# 棋盘快照
def get_board_snapshot(self):
return self._board[:]

# 取棋盘上的合法走法
def get_legal_actions(self):
actions = []
for i in range(9):
if self._board[i] == '-':
actions.append(i)
return actions

# 判断走法是否合法
def is_legal_action(self, action):
return self._board[action] == '-'

# 终止检测
def teminate(self):
board = self._board
lines = [board[0:3], board[3:6], board[6:9], board[0::3], board[1::3], board[2::3], board[0::4], board[2:7:2]]

if ['X']*3 in lines or ['O']*3 in lines or '-' not in board:
return True
else:
return False

# 胜负检查
def get_winner(self):
board = self._board
lines = [board[0:3], board[3:6], board[6:9], board[0::3], board[1::3], board[2::3], board[0::4], board[2:7:2]]

if ['X']*3 in lines:
return 0
elif ['O']*3 in lines:
return 1
else:
return 2

# 打印棋盘
def print_b(self):
board = self._board
for i in range(len(board)):
print(board[i], end='')
if (i+1)%3 == 0:
print()

# 打印棋谱
def print_history(self):
print(self._history)

# 玩家
class Player(object):
'''
玩家只做两件事：思考、落子
1. 思考 --> 得到走法
2. 落子 --> 执行走法，改变棋盘
'''
def __init__(self, take='X'): # 默认执的棋子为 take = 'X'
self.take=take

def think(self, board):
pass

def move(self, board, action):
board._move(action, self.take)

# 人类玩家
class HumanPlayer(Player):
def __init__(self, take):
super().__init__(take)

def think(self, board):
while True:
action = input('Please input a num in 0-8:')
if len(action)==1 and action in '012345678' and board.is_legal_action(int(action)):
return int(action)

# 电脑玩家
class AIPlayer(Player):
def __init__(self, take):
super().__init__(take)

def think(self, board):
print('AI is thinking ...')
take = ['X','O'][self.take=='X']
player = AIPlayer(take)     # 假想敌！！！
_, action = self.minimax(board, player)
#print('OK')
return action

# 极大极小法搜索，α-β剪枝
def minimax(self, board, player, depth=0) :
'''参考：https://stackoverflow.com/questions/44089757/minimax-algorithm-for-tic-tac-toe-python'''
if self.take == "O":
bestVal = -10
else:
bestVal = 10

if board.teminate() :
if board.get_winner() == 0 :
return -10 + depth, None
elif board.get_winner() == 1 :
return 10 - depth, None
elif board.get_winner() == 2 :
return 0, None

for action in board.get_legal_actions() : # 遍历合法走法
board._move(action, self.take)
val, _ = player.minimax(board, self, depth+1) # 切换到 假想敌！！！
board._unmove(action) # 撤销走法，回溯

if self.take == "O" :
if val > bestVal:
bestVal, bestAction = val, action
else :
if val < bestVal:
bestVal, bestAction = val, action

return bestVal, bestAction

# 游戏
class Game(object):
def __init__(self):
self.board = Board()
self.current_player = None

# 生成玩家
def mk_player(self, p, take='X'): # p in [0,1]
if p==0:
return HumanPlayer(take)
else:
return AIPlayer(take)

# 切换玩家
def switch_player(self, player1, player2):
if self.current_player is None:
return player1
else:
return [player1, player2][self.current_player == player1]

# 打印赢家
def print_winner(self, winner): # winner in [0,1,2]
print(['Winner is player1','Winner is player2','Draw'][winner])

# 运行游戏
def run(self):
ps = input("Please select two player's type:\n\t0.Human\n\t1.AI\nSuch as:0 0\n")
p1, p2 = [int(p) for p in ps.split(' ')]
player1, player2 = self.mk_player(p1, 'X'), self.mk_player(p2, 'O') # 先手执X，后手执O

print('\nGame start!\n')
self.board.print_b() # 显示棋盘
while True:
self.current_player = self.switch_player(player1, player2) # 切换当前玩家

action = self.current_player.think(self.board) # 当前玩家对棋盘进行思考后，得到招法

self.current_player.move(self.board, action)   # 当前玩家执行招法，改变棋盘

self.board.print_b() # 显示当前棋盘

if self.board.teminate(): # 根据当前棋盘，判断棋局是否终止
winner = self.board.get_winner() # 得到赢家 0,1,2
break

self.print_winner(winner)
print('Game over!')

self.board.print_history()

if __name__ == '__main__':
Game().run()

效果图

下图是人人对战的结果