tictactoe.txt

import random

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 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(' ' + board[4] + ' | ' + board[5] + ' | ' + board[6])
    print('-----------')
    print('   |   |')
    print(' ' + board[1] + ' | ' + board[2] + ' | ' + board[3])

def playAgain():
# This function returns True if the player wants to play again, otherwise it returns False.
    print('Do you want to play again? (y or n)')
    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 for board and le for letter so we don’t have to type as much.
    return ((bo[7] == le and bo[8] == le and bo[9] == le) or #across 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[int(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('Enter 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