tictactoe.py

class TicTacToe:  
    def __init__(self):  
        self.board = [[' ']*3 for _ in range(3)]  
        self.player = 'X'  

    def print_board(self):  
        for row in self.board:  
            print(' | '.join(row))  
            print('-' * 5)  

    def is_winner(self, player):  
        for row in self.board:  
            if all(cell == player for cell in row): return True  
        for col in zip(*self.board):  
            if all(cell == player for cell in col): return True  
        if all(self.board[i][i] == player for i in range(3)) or all(self.board[i][2-i] == player for i in range(3)):  
            return True  
        return False  

    def is_draw(self):  
        return all(cell != ' ' for row in self.board for cell in row)  

    def dfs(self, player):  
        if self.is_winner('X'): return 1  
        if self.is_winner('O'): return -1  
        if self.is_draw(): return 0  

        best_score = -float('inf') if player == 'X' else float('inf')  
        for i in range(3):  
            for j in range(3):  
                if self.board[i][j] == ' ':  
                    self.board[i][j] = player  
                    score = self.dfs('O' if player == 'X' else 'X')  
                    self.board[i][j] = ' '  
                    if (player == 'X' and score > best_score) or (player == 'O' and score < best_score):  
                        best_score = score  
        return best_score  

    def play(self):  
        while True:  
            self.print_board()  
            if self.is_winner('X') or self.is_winner('O') or self.is_draw():  
                print("Game Over.")  
                if self.is_winner('X'): print("Player X wins!")  
                elif self.is_winner('O'): print("Player O wins!")  
                else: print("It's a draw!")  
                break  

            if self.player == 'X':  
                best_move = None  
                best_score = -float('inf')  
                for i in range(3):  
                    for j in range(3):  
                        if self.board[i][j] == ' ':  
                            self.board[i][j] = 'X'  
                            score = self.dfs('O')  
                            self.board[i][j] = ' '  
                            if score > best_score:  
                                best_score = score  
                                best_move = (i, j)  
                if best_move:  
                    self.board[best_move[0]][best_move[1]] = 'X'  
            else:  
                while True:  
                    try:  
                        r = int(input("Row (0-2): "))  
                        c = int(input("Col (0-2): "))  
                        if self.board[r][c] == ' ':  
                            self.board[r][c] = 'O'  
                            break  
                        print("Taken!")  
                    except (ValueError, IndexError):  
                        print("Invalid!")  
            self.player = 'O' if self.player == 'X' else 'X'  

if __name__ == '__main__':  
    TicTacToe().play()