tictactoe.py

class Board(list):
	def __init__(self):
		for i in range(9):
			self.append('-')
	def isWin(self):
		'''
		Returns true if either player is winning else returns false
		'''
		# check if any of the rows has winning combination
		for i in range(3):
			if len(set(self[i*3:i*3+3])) == 1 and self[i*3] != '-': return True
		# check if any of the Columns has winning combination
		for i in range(3):
			if self[i]==self[i+3]==self[i+6] and self[i] != '-':
				return True
		# check diagonals
		if self[0] is self[4] and self[4] is self[8] and self[4] is not '-':
			return  True
		if self[2]==self[4]==self[6] and self[4] is not '-':
			return  True
		return False
	def __str__(self):
		return ''.join( (str(i) if self[i]=='-' else self[i]) + ('\n' if i%3==2 else ' | ') for i in range(len(self)))
		
class Player(object):
	def __init__(self, piece, cpu):
		self.piece = piece
		self.cpu = cpu
	def move(self, board):
		if self.cpu:
			print "CPU (%s) is moving ..."%(self.piece)
			return AIMove(board, self.piece)[1]
		else:
			while True:
				coords = raw_input('Player\'s move (%s): '%self.piece)
				return int(coords)
		
def AIMove(board, player):
	"""
	Arguments:
	board: list containing X,- and O
	player: one character string 'X' or 'O'
 
	Returns:
	willwin: 1 if 'X' is winning, 0 if the game is draw and -1 if 'O' is winning
	nextmove: best player move else -1 if game is over
	"""
	#Return early if blank board
	if len(set(board)) == 1: return 0,4
	#Check for winner
	if board.isWin() :
		if player is 'X': return -1,-1
		else: return 1,-1
	#Check for tie
	if board.count('-') == 0: return 0,-1
	#Get possible moves
	possible_moves = []
	for i in range(len(board)):
		if board[i] == '-':
			possible_moves.append(i)
	#determine next player
	nextplayer = 'X' if player=='O' else 'O'
	#Iterate over possible moves using minimax algorithm
	results = []
	for i in possible_moves:
		board[i] = player
		result, move = AIMove(board,nextplayer)
		results.append(result)
		board[i] = '-'
	if player == 'X':
		max_result = max(results)
		return max_result, possible_moves[results.index(max_result)]
	else:
		min_result=min(results)
		return min_result, possible_moves[results.index(min_result)]
def play():
	print ">>> Welcome to Boss Tic Tac Toe! <<<"
	gameboard = Board()
	players = [Player('X', False), Player('O', True)]
	current_player = 0
	print str(gameboard)
	while not gameboard.isWin():
		gameboard[players[current_player].move(gameboard)] = players[current_player].piece
		print str(gameboard)
		current_player += 1
		if current_player > 1: current_player = 0
play()