tictactoe.py

#!/usr/bin/python3 

class TicTacToeGame():
    def __init__(self):
        # Our game state is defined by a list of 3 lists, each containing 3
        # characters, which can be either ' ' (blank), an 'X', or an 'O'.
        self.state = [[' ', ' ', ' '], [' ', ' ', ' '], [' ', ' ', ' ']]
        self.next_turn_player = 'X'
    
    def do_move(self, index):
        """
        Plays a move at the given index (beginning with 1 in the top-left).
        """
        # Correct to zero-indexing
        index -= 1
        
        # Make sure the move index is not out of bounds
        if index >= 9 or index < 0:
            raise IndexError
        
        # Find the row/column
        row = index // 3
        col = index % 3
        
        # Make sure the position hasn't been played yet
        if self.state[row][col] != ' ':
            raise ValueError
        
        # Make the move
        self.state[row][col] = self.next_turn_player
        
        # Update the player expected for next turn
        self.next_turn_player = ('O' if self.next_turn_player == 'X' else 'X')
    
    def __repr__(self):
        """
        Returns the representation of the game state as a string, which looks
        like this:
        
        1 |2 |3
          |  |
        --------
        4 |\/|6
          |/\|
        --------
        7 |/\|9 
          |\/|  
        
        """
        representation = []
        i = 0
        for row in self.state:
            upper_halves = []
            lower_halves = []
            for item in row:
                i += 1
                if item == 'X':
                    upper_halves.append('\\/')
                    lower_halves.append('/\\')
                elif item == 'O':
                    upper_halves.append('/\\')
                    lower_halves.append('\\/')
                else:
                    upper_halves.append('%i ' % i)
                    lower_halves.append('  ')
            representation += ['|'.join(upper_halves) + '\n' +
                               '|'.join(lower_halves) + '\n']
        return '--------\n'.join(representation)
    
    def check_game_end(self):
        """Checks the game state to see if the game is over, either by virtue of
           someone winning or because all spaces are filled."""
        
        # Assume the board is filled until contrary evidence
        filled = True
        for row in self.state:
            if ' ' in row:
                filled = False
                break
        
        # If there is a winner, then one of the following sets of indices in
        # our game state will all be the same value:
        wins = (# Horizontal wins:
                (0, 1, 2),
                (3, 4, 5),
                (6, 7, 8),
                # Vertical wins:
                (0, 3, 6),
                (1, 4, 7),
                (2, 5, 8),
                # Diagonal wins:
                (0, 4, 8),
                (2, 4, 6))
        
        for win in wins:
            i, j, k = win
            a, b, c = (self.state[i // 3][i % 3],
                       self.state[j // 3][j % 3],
                       self.state[k // 3][k % 3])
            if a == b and b == c and a != ' ':
                return a
        
        return filled
    
    def play_2p_game(self):
        """
        Two-Player Interactive Game
        This method creates a loop which waits for input from the command line.
        After each move is played, it shows the new state of the game. This
        continues until the game is over.
        """
        print(self)
        while True:
            index = input('Player %s move: ' % self.next_turn_player)
            try:
                self.do_move(int(index))
            except TypeError:
                print('Expected a position number')
            except IndexError:
                print('Position out of range')
            except ValueError:
                print('Position already played')
            else:
                print(self)
                end_state = self.check_game_end()
                if end_state == True:
                    print('Tied game.')
                    break
                elif end_state:
                    print('Player %s wins!' % end_state)
                    break
    
    def play_1p_game(self):
        """
        One-Player Interactive Game
        Like the two-player game, except now we play against an AI.
        """
        pass

ttt = TicTacToeGame()
ttt.play_2p_game()