用python编写一个字符界面的五子棋人机对战程序。

好的，接下来我将给您提供一个简单的五子棋人机对战程序的示例代码，仅供参考。

import os

# 定义棋盘大小
BOARD_SIZE = 15

# 定义棋子类型
PLAYER_CHESS = '●'
AI_CHESS = '○'
EMPTY_CHESS = ' '

# 创建一个空棋盘
def create_board():
    board = []
    for i in range(BOARD_SIZE):
        row = [EMPTY_CHESS] * BOARD_SIZE
        board.append(row)
    return board

# 打印当前棋盘
def print_board(board):
    # 打印列标记
    print('   ', end='')
    for i in range(BOARD_SIZE):
        print(chr(i+ord('A')), end=' ')
    print()

    # 打印行标记和棋盘
    for i in range(BOARD_SIZE):
        print(' %2d' % (i+1), end=' ')
        for j in range(BOARD_SIZE):
            print(board[i][j], end=' ')
        print()

# 判断某个位置是否可以下棋
def is_valid_move(board, row, col):
    return board[row][col] == EMPTY_CHESS

# 下棋
def make_move(board, row, col, chess):
    board[row][col] = chess

# 悔棋
def undo_move(board, row, col):
    board[row][col] = EMPTY_CHESS

# 判断某个位置是否连成五子
def is_five(board, row, col):
    chess = board[row][col]
    if chess == EMPTY_CHESS:
        return False

    # 水平方向
    count = 1
    for i in range(1, 5):
        if col-i < 0 or board[row][col-i] != chess:
            break
        count += 1
    for i in range(1, 5):
        if col+i >= BOARD_SIZE or board[row][col+i] != chess:
            break
        count += 1
    if count >= 5:
        return True

    # 垂直方向
    count = 1
    for i in range(1, 5):
        if row-i < 0 or board[row-i][col] != chess:
            break
        count += 1
    for i in range(1, 5):
        if row+i >= BOARD_SIZE or board[row+i][col] != chess:
            break
        count += 1
    if count >= 5:
        return True

    # 左上到右下方向
    count = 1
    for i in range(1, 5):
        if row-i < 0 or col-i < 0 or board[row-i][col-i] != chess:
            break
        count += 1
    for i in range(1, 5):
        if row+i >= BOARD_SIZE or col+i >= BOARD_SIZE or board[row+i][col+i] != chess:
            break
        count += 1
    if count >= 5:
        return True

    # 左下到右上方向
    count = 1
    for i in range(1, 5):
        if row+i >= BOARD_SIZE or col-i < 0 or board[row+i][col-i] != chess:
            break
        count += 1
    for i in range(1, 5):
        if row-i < 0 or col+i >= BOARD_SIZE or board[row-i][col+i] != chess:
            break
        count += 1
    if count >= 5:
        return True

    return False

# 判断棋局是否结束
def is_game_over(board):
    for i in range(BOARD_SIZE):
        for j in range(BOARD_SIZE):
            if is_valid_move(board, i, j) and (is_five(board, i, j, PLAYER_CHESS) or is_five(board, i, j, AI_CHESS)):
                return True
    return False

# AI下棋
def ai_move(board):
    # 找到所有可以下棋的位置
    candidates = []
    for i in range(BOARD_SIZE):
        for j in range(BOARD_SIZE):
            if is_valid_move(board, i, j):
                candidates.append((i, j))

    # 评估每个位置的得分，并选出最高分的位置作为AI下棋的位置
    best_score = -1
    best_move = None
    for move in candidates:
        row, col = move
        score = evaluate_move(board, row, col, AI_CHESS)
        if score > best_score:
            best_score = score
            best_move = move

    return best_move

# 评估某个位置的得分
def evaluate_move(board, row, col, chess):
    # 评估在该位置下棋后，横向、竖向、左上到右下、右上到左下四个方向上的连子数量
    count1 = count2 = count3 = count4 = 0
    for i in range(1, 5):
        if col-i < 0 or board[row][col-i] != chess:
            break
        count1 += 1
    for i in range(1, 5):
        if col+i >= BOARD_SIZE or board[row][col+i] != chess:
            break
        count1 += 1

    for i in range(1, 5):
        if row-i < 0 or board[row-i][col] != chess:
            break
        count2 += 1
    for i in range(1, 5):
        if row+i >= BOARD_SIZE or board[row+i][col] != chess:
            break
        count2 += 1

    for i in range(1, 5):
        if row-i < 0 or col-i < 0 or board[row-i][col-i] != chess:
            break
        count3 += 1
    for i in range(1, 5):
        if row+i >= BOARD_SIZE or col+i >= BOARD_SIZE or board[row+i][col+i] != chess:
            break
        count3 += 1

    for i in range(1, 5):
        if row+i >= BOARD_SIZE or col-i < 0 or board[row+i][col-i] != chess:
            break
        count4 += 1
    for i in range(1, 5):
        if row-i < 0 or col+i >= BOARD_SIZE or board[row-i][col+i] != chess:
            break
        count4 += 1

    # 根据连子数量计算得分
    score = max(count1, count2, count3, count4)
    return score

# 主函数
def main():
    # 创建一个空棋盘
    board = create_board()

    # 打印棋盘
    print_board(board)

    # 循环下棋
    while True:
        # 玩家下棋
        while True:
            move = input('请下棋（例如：A3）：')
            if len(move) == 2 and move[0].isalpha() and move[1].isdigit():
                col = ord(move[0]) - ord('A')
                row = int(move[1:]) - 1
                if is_valid_move(board, row, col):
                    make_move(board, row, col, PLAYER_CHESS)
                    break
            print('无效的位置，请重新输入！')

        # 打印棋盘
        os.system('cls' if os.name == 'nt' else 'clear')
        print_board(board)

        # 判断游戏是否结束
        if is_game_over(board):
            print('游戏结束，你赢了！')
            break

        # AI下棋
        row, col = ai_move(board)
        make_move(board, row, col, AI_CHESS)

        # 打印棋盘
        os.system('cls' if os.name == 'nt' else 'clear')
        print_board(board)

        # 判断游戏是否结束
        if is_game_over(board):
            print('游戏结束，你输了！')
            break

# 启动主函数
if __name__ == '__main__':
    main()

该程序采用了简单的极大极小算法来实现AI下棋的策略，如果您需要更高级的算法，可以参考其他资料。