TicTacToe和Minimax

Question

我是一个年轻的程序员，正在学习python并努力实现AI（使用minimax）来玩TicTacToe。我开始在线观看教程，但是该教程使用的是JavaScript，因此无法解决我的问题。我也查看了这个问题（Python minimax for tictactoe），但是它没有任何答案，实现与我的有很大不同。

这是我的代码：

board = [" ", " ", " ", " ", " ", " ", " ", " ", " "]

playerSymbol = ""
playerPosition = []

aiSymbol = ""
aiPosition = []

global score

possiblePositions = [0, 1, 2, 3, 4, 5, 6, 7, 8]
winner = None

scoreBoard = {
    playerSymbol: 1,
    aiSymbol: -1,
    "tie": 0
}
turn = 0


def drawBoard():
    print(board[0] + " | " + board[1] + " | " + board[2])
    print("___" + "___" + "___")
    print(board[3] + " | " + board[4] + " | " + board[5])
    print("___" + "___" + "___")
    print(board[6] + " | " + board[7] + " | " + board[8])


def choice():
    global playerSymbol
    global aiSymbol

    answer = input("What do you want to play as? (type x or o) ")

    if answer.upper() == "X":
        playerSymbol = "X"
        aiSymbol = "O"
    else:
        playerSymbol = "O"
        aiSymbol = "X"


def won():
    global winner
    winningPositions = [{0, 1, 2}, {3, 4, 5}, {6, 7, 8}, {0, 4, 8}, {2, 4, 6}, {0, 3, 6}, {1, 4, 7}, {2, 5, 8}]

    for position in winningPositions:
        if position.issubset(playerPosition):
            winner = playerSymbol
            print("Player Wins :)")
            return True
        elif position.issubset(aiPosition):
            winner = aiSymbol
            print("AI wins :(")
            return True
    if len(possiblePositions) == 0:
        winner = "tie"
        print("Guess it's a draw")
        return True

    return False


def findOptimalField(field):
    global score
    sampleScore = -1000
    for i in range(9):
        if field[i] == " ":
            field[i] = aiSymbol
            score = minimax(field, 0, False)
            field[i] = " "
            if score > sampleScore:
                sampleScore = score
                optimalMove = i

    return optimalMove


def minimax(field, depth, isMaximizing):
    global scoreBoard
    global score
    global winner

    if winner is not None:
        return scoreBoard[winner]

    if isMaximizing:
        bestScore = -1000
        for i in range(9):
            if field[i] == " ":
                field[i] = aiSymbol
                score = minimax(field, depth + 1, False)
                field[i] = " "
                bestScore = max(score, bestScore)
        return bestScore
    else:
        otherBestScore = 1000
        for i in range(9):
            if field[i] == " ":
                field[i] = playerSymbol
                score = minimax(field, depth + 1, True)
                field[i] = " "
                otherBestScore = min(score, otherBestScore)
        return otherBestScore


def play(field):
    global turn
    global score
    choice()

    optimalMove = 0

    while not won():
        if turn % 2 == 0:
            pos = int(input("Where would you like to play? (0-8) "))
            possiblePositions.remove(pos)
            playerPosition.append(pos)
            field[pos] = playerSymbol
            turn += 1
            drawBoard()
        else:
            aiTurn = findOptimalField(field)
            possiblePositions.remove(aiTurn)
            aiPosition.append(aiTurn)
            field[aiTurn] = aiSymbol
            turn += 1
            print("\n")
            print("\n")
            drawBoard()
    else:
        print("Thanks for playing :)")


play(board)

我一直遇到问题：UnboundLocalError：赋值之前引用的局部变量'optimalMove'，我认为这是由于分数从不大于> sampleScore。除非另有声明，否则这可能是Python逻辑将每个变量解释为局部变量的结果。我来自Java背景，并不习惯：（

但是，我愿意提出建议和方法来改进我的代码并修复此错误。预先感谢并保持健康，克里斯蒂

Answer 1

更改此部分，即使它不在optimalMove内部，您的实现也会返回if statement。

    if score > sampleScore:
        sampleScore = score
        optimalMove = i
        return optimalMove