井字棋python代码注释

以下是井字棋Python代码的注释：

# Tic-Tac-Toe 井字棋游戏

# 全局常量
X = "X"
O = "O"
EMPTY = " "

# 询问是否继续
def ask_yes_no(question):
    response = None
    while response not in ("y", "n"):
        response = input(question).lower()
    return response

# 询问玩家下棋位置
def ask_number(question, low, high):
    response = None
    while response not in range(low, high):
        response = int(input(question))
    return response

# 询问玩家选择棋子
def pieces():
    go_first = ask_yes_no("你想先手吗？(y/n): ")
    if go_first == "y":
        print("\n你先手！")
        human = X
        computer = O
    else:
        print("\n我先手！")
        computer = X
        human = O
    return computer, human

# 新建棋盘
def new_board():
    board = []
    for square in range(9):
        board.append(EMPTY)
    return board

# 显示棋盘
def display_board(board):
    print("\n\t", board[0], "|", board[1], "|", board[2])
    print("\t", "---------")
    print("\t", board[3], "|", board[4], "|", board[5])
    print("\t", "---------")
    print("\t", board[6], "|", board[7], "|", board[8], "\n")

# 判断胜者
def winner(board):
    WAYS_TO_WIN = ((0, 1, 2),
                   (3, 4, 5),
                   (6, 7, 8),
                   (0, 3, 6),
                   (1, 4, 7),
                   (2, 5, 8),
                   (0, 4, 8),
                   (2, 4, 6))
    for row in WAYS_TO_WIN:
        if board[row[0]] == board[row[1]] == board[row[2]] != EMPTY:
            winner = board[row[0]]
            return winner
    if EMPTY not in board:
        return "Tie"
    return None

# 询问玩家下棋位置
def human_move(board, human):
    legal = legal_moves(board)
    move = None
    while move not in legal:
        move = ask_number("你的下棋位置(0-8):", 0, 9)
        if move not in legal:
            print("\n这个位置已经被占了，请重新选择。\n")
    print("好的...")
    return move

# 计算AI下棋位置
def computer_move(board, computer, human):
    # 复制一份棋盘，以免影响原棋盘
    board = board[:]
    # AI下棋位置的优先级
    BEST_MOVES = (4, 0, 2, 6, 8, 1, 3, 5, 7)
    print("我选择了位置", end=" ")
    # 如果AI能赢，就下在那个位置
    for move in legal_moves(board):
        board[move] = computer
        if winner(board) == computer:
            print(move)
            return move
        # 撤销这个位置的选择
        board[move] = EMPTY
    # 如果玩家能赢，就下在那个位置
    for move in legal_moves(board):
        board[move] = human
        if winner(board) == human:
            print(move)
            return move
        # 撤销这个位置的选择
        board[move] = EMPTY
    # 如果都不能赢，就下在最优先的位置
    for move in BEST_MOVES:
        if move in legal_moves(board):
            print(move)
            return move

# 获取合法的下棋位置
def legal_moves(board):
    moves = []
    for square in range(9):
        if board[square] == EMPTY:
            moves.append(square)
    return moves

# 主函数
def main():
    computer, human = pieces()
    board = new_board()
    display_board(board)
    while not winner(board):
        if computer == X:
            move = computer_move(board, computer, human)
            board[move] = computer
        else:
            move = human_move(board, human)
            board[move] = human
        display_board(board)
    the_winner = winner(board)
    if the_winner == "Tie":
        print("平局！")
    else:
        print("胜利者是：", the_winner, "！")
        if the_winner == computer:
            print("我赢了！")
        else:
            print("你赢了！")

# 运行主函数
main()