tictactoe2.py

# Tic Tac Toe



import random



def 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():

   # Lets the player type which letter they want to be.

    # 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 = input().upper()


    # the first element in the list 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 input().lower().startswith('y')


def makeMove(board, letter, move):

    board[move] = letter


def 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)) # diagonal


def getBoardCopy(board):

    # Make a duplicate of the board list and return it the duplicate.

    dupeBoard = []


    for i in board:

        dupeBoard.append(i)


    return dupeBoard


def 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 = 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 None


def 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, 10):

        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, 10):

        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 True



print('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