# Tic Tac Toeimport randomdef drawBoard(board):# This function prints out the board that it was passed.# "board" is a list of 10 strings representing the board (ignore index 0) print ' | |' print ' ' + board[7] + ' | ' + board[8] + ' | ' + board[9] print ' | |' print '-----------' print ' | |' print ' ' + board[4] + ' | ' + board[5] + ' | ' + board[6] print ' | |' print '-----------' print ' | |' print ' ' + board[1] + ' | ' + board[2] + ' | ' + board[3] print ' | |'def inputPlayerLetter(): # Let's the player type which letter they want to # Returns a list with the player's letter as the first item, and the computer's letter as the second. letter = '' while not (letter == 'X' or letter == 'O'): print 'Do you want to be X or O?' letter = raw_input().upper() # the first element in the tuple is the player's letter, the second is the computer's letter. if letter == 'X': return ['X', 'O'] else: return ['O', 'X']def whoGoesFirst(): # Randomly choose the player who goes first. if random.randint(0, 1) == 0: return 'computer' else: return 'player'def playAgain(): # This function returns True if the player wants to play again, otherwise it returns False. print 'Do you want to play again? (yes or no)' return raw_input().lower().startswith('y')def makeMove(board, letter, move): board[move] = letterdef isWinner(bo, le): # Given a board and a player's letter, this function returns True if that player has won. # We use bo instead of board and le instead of letter so we don't have to type as much. return ((bo[7] == le and bo[8] == le and bo[9] ==le) or # across the top (bo[4] == le and bo[5] == le and bo[6] == le) or # across the middle (bo[1] == le and bo[2] == le and bo[3] == le) or #across the bottom (bo[7] == le and bo[4] == le and bo[1] == le) or # down the left side (bo[8] == le and bo[5] == le and bo[2] == le) or #down the middle (bo[9] == le and bo[6] == le and bo[3] == le) or #down the right side (bo[7] == le and bo[5] == le and bo[3] == le) or #diagonal (bo[9] == le and bo[5] == le and bo[1] == le)) # diagonaldef getBoardCopy(board): # Make a duplicate of the board list and return it the duplicate. dupeBoard = [] for i in board: dupeBoard.append(i) return dupeBoarddef isSpaceFree(board, move): # Return true if the passed move is free on the passed board. return board[move] == ' 'def getPlayerMove(board): # Let the player type in their move. move = ' ' while move not in '1 2 3 4 5 6 7 8 9'.split() or not isSpaceFree(board, int(move)): print 'What is your next move? (1-9)' move = raw_input() return int(move)def chooseRandomMoveFromList(board, movesList): # Returns a valid move from the passed list on the passed board. # Returns None if there is no valid move. possibleMoves = [] for i in movesList: if isSpaceFree(board, i): possibleMoves.append(i) if len(possibleMoves) != 0: return random.choice(possibleMoves) else: return Nonedef getComputerMove(board, computerLetter): # Given a board and the computer's letter, determine where to move and return that move. if computerLetter == 'X': playerLetter = 'O' else: playerLetter = 'X' # Here is our algorithm for our Tic Tac Toe AI: # First, check if we can win in the next move for i in range(1, 9): copy = getBoardCopy(board) if isSpaceFree(copy, i): makeMove(copy, computerLetter, i) if isWinner(copy, computerLetter): return i # Check if the player could win on their next move, and block them. for i in range(1, 9): copy = getBoardCopy(board) if isSpaceFree(copy, i): makeMove(copy, playerLetter, i) if isWinner(copy, playerLetter): return i # Try to take one of the corners, if they are free. move = chooseRandomMoveFromList(board, [1, 3, 7, 9]) if move != None: return move # Try to take the center, if it is free. if isSpaceFree(board, 5): return 5# Move on one of the sides. return chooseRandomMoveFromList(board, [2, 4, 6, 8])def isBoardFull(board): # Return True if every space on the board has been taken. Otherwise return False. for i in range(1, 10): if isSpaceFree(board, i): return False return Trueprint 'Welcome to Tic Tac Toe!'while True: # Reset the board theBoard = [' '] * 10 playerLetter, computerLetter = inputPlayerLetter() turn = whoGoesFirst() print 'The ' + turn + ' will go first.' gameIsPlaying = True while gameIsPlaying: if turn == 'player': # Player's turn. drawBoard(theBoard) move = getPlayerMove(theBoard) makeMove(theBoard, playerLetter, move) if isWinner(theBoard, playerLetter): drawBoard(theBoard) print 'Hooray! You have won the game!' gameIsPlaying = False else: if isBoardFull(theBoard): drawBoard(theBoard) print 'The game is a tie!' break else: turn = 'computer' else:# Computer's turn. move = getComputerMove(theBoard, computerLetter) makeMove(theBoard, computerLetter, move) if isWinner(theBoard, computerLetter): drawBoard(theBoard) print 'The computer has beaten you! You lose.' gameIsPlaying = False else: if isBoardFull(theBoard): drawBoard(theBoard) print 'The game is a tie!' break else: turn = 'player' if not playAgain(): break