tictactoe.py

# Command-line Tic Tac Toe for two humans written in Python.
# Play in a terminal by running 'python tictactoe.py'.


boxes = [ ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ]
player_X = 'X'
player_0 = '0'
first_player = player_X
turn = 1
winning_combos = [  [0, 1, 2], [3, 4, 5], [6, 7, 8], [0, 3, 6],
                    [1, 4, 7], [2, 5, 8], [0, 4, 8], [2, 4, 6], ]


def print_board(initial=False):
    """ Print the game board. If this is the beginning of the game,
        print out 1-9 in the boxes to show players how to pick a
        box. Otherwise, update each box with X or 0 from boxes[].
    """
    print('''
             {} | {} | {} 
            -----------
             {} | {} | {}
            -----------
             {} | {} | {} 
        ''').format(*([x for x in range(1, 10)] if initial else boxes))


def take_turn(player, turn):
    """ Create a loop that keeps asking the current player for
        their input until a valid choice is made.
    """
    while True:
        box = raw_input('Player %s, type a number from 1-9 to select a box: ' % player)

        try:
            box = int(box) - 1 # subtract 1 to sync with boxes[] index numbers
        except ValueError:
            # Not an integer
            print('That\'s not a valid number, try again.\n')
            continue

        if 0 <= box <= 8:
            if boxes[box] == ' ': # initial value
                boxes[box] = player # set to value of current player
                break
            else:
                print('That box is already marked, try again.\n')
                continue
        else:
            print('That number is out of range, try again.\n')
            continue


def switch_player(turn):
    """ Switch the player based on how many moves have been made.
        X starts the game so if this turn # is even, it's 0's turn. 
    """
    current_player = player_0 if turn % 2 == 0 else player_X
    return current_player


def check_for_win(player, turn):
    """ Check for a win (or a tie). For each combo in winning_combos[],
        count how many of its corresponding squares have the current 
        player's mark. If a player's score count reaches 3, return a win.
        If it doesn't, and this is already turn # 9, return a tie. If
        neither, return False so the game continues.
    """
    win = False
    tie = False
    if turn > 4: # need at least 5 moves before a win is possible
        for combo in winning_combos:
            score = 0
            for index in combo:
                if boxes[index] == player:
                    score += 1
                if score == 3:
                    win = True

        if turn == 9:
            tie = True

    return win, tie


def play(player, turn):
    """ Create a loop that keeps the game in play
        until it ends in a win or tie
    """
    while True:
        take_turn(player, turn)
        print_board()
        win, tie = check_for_win(player, turn)
        if win or tie:
            if win:
                print('Game over. %s wins!\n' % player)
            else:
                print('Game over. It\'s a tie.\n')
            break
        turn += 1
        player = switch_player(turn)


# Begin the game: 
print('\n\nWelcome to Tic Tac Toe for two humans!')
print_board(initial=True)
play(first_player, turn)