aili.py

##########################################################
# Global variables and functions directly related to them.

currentPlayer = 'X'
board = ['_' for i in range(9)]
done = 0

def i(x, y):
    return y*3 + x

def printBoard(board):
    print("")
    print("   0 1 2 ")
    print("   _____ ")
    for i in range(3):
        print("{0} |{1} {2} {3}|".format(i, board[i*3], board[i*3+1], board[i*3+2]))
    print("")

def swapCurrentPlayer():
    global currentPlayer
    if currentPlayer == 'X':
        currentPlayer = 'O'
    else:
        currentPlayer = 'X'


#######################################################
# Ai related functions. Includes Minimax implementation

def minimax(player, board):
    if hasWon(board):
        return player*-1
    if isFull(board):
        return 0

    children = allLegalMoves(board)

    if player == 1:
        maximum = -2
        for move in children:
            temp = minimax(-1*player, expandChild(board, move, player))
            if temp > maximum:
                maximum = temp
        return maximum

    else:
        minimum = 2
        for move in children:
            temp = minimax(-1*player, expandChild(board, move, player))
            if temp < minimum:
                minimum = temp
        return minimum

def allLegalMoves(board):
    moves = []
    for i in range(9):
        if isVacant(board, i):
            moves.append(i)
    return moves

def isVacant(board, i):
    if board[i] != '_':
        return 0
    return 1

def expandChild(board, move, player):
    piece = 'X'
    newBoard = board[:]

    if player == -1:
        piece = 'O'

    newBoard[move] = piece
    return newBoard


########################################
# Functions to determine if game is over

def checkGameEnded(player, board):
    global done
    if hasWon(board):
        done = 1
        if player == 'X':
            print("Aili has won!")
        else:
            print("You hvae won!")
    if isFull(board):
        done = 1
        print("Game ended with a tie.")

def isFull(board):
    n = 0

    for i in range(9):
        n += not isVacant(board, i)

    return n >= 9

def hasWon(board):
    returnVal = 0
    returnVal += threeInRow(board, 0, 4, 8)
    returnVal += threeInRow(board, 2, 4, 6)

    for i in range(3):
        n = i*3
        returnVal += threeInRow(board, n, n+1, n+2)
        returnVal +=  threeInRow(board, i, i+3, i+6)
    return returnVal

def threeInRow(board, i, j, k):
    if board[i] != '_' and board[j] != '_' and board[k] != '_' and board[i] == board[j] and board[i] == board[k]:
        return 1
    return 0


#############################################
# Piece placement functions for player and Ai

def aiMove(board):
    print("Aili makes her move.")
    maxMove = -1
    maximum = -2
    children = allLegalMoves(board)

    for move in children:
        temp = minimax(-1, expandChild(board, move, 1))
        if temp > maximum:
            maximum = temp
            maxMove = move
    return maxMove

def userMove(board):
    while 1:
        userInput = input("{0}'s turn: ".format('O'))
        x = int(userInput.split(' ')[0])%3
        y = int(userInput.split(' ')[1])%3

        if i(x, y) in allLegalMoves(board):
            return i(x, y)
        else:
            print("Place is not vacant.")

def placePiece(player, board):
    move = 0
    if player == 'X':
        move = aiMove(board)
    else:
        move = userMove(board)
    board[move] = player
    printBoard(board)


##################################
# Game loop and intro print-screen

print(" __________________________")
print("|                          |")
print("|       /\  |  |   |       |")
print("|      /  \ |  |__ |       |")
print("|                          |")
print("|The tic tac toe playing AI|")

printBoard(board)

while not done:
    placePiece(currentPlayer, board)
    checkGameEnded(currentPlayer, board)
    swapCurrentPlayer()