TIC TAC TOE

game.py

import random


def draw_board(board):
    print('   |   |')
    print(' %s | %s | %s' % (board[1], board[2], board[3]))
    print('   |   |')
    print('---+---+---')
    print('   |   |')
    print(' %s | %s | %s' % (board[4], board[5], board[6]))
    print('   |   |')
    print('---+---+---')
    print('   |   |')
    print(' %s | %s | %s' % (board[7], board[8], board[9]))
    print('   |   |')


def input_player_letter():
    letter = ''
    while not (letter == 'X' or letter == 'O'):
        print('Choose X or O:')
        letter = input().upper()

    # the first element in the lsit is the player's letter
    if letter == 'X':
        return ['X', 'O']
    else:
        return ['O', 'X']


def who_goes_first():
    if random.randint(0, 1) == 0:
        return 'computer'
    else:
        return 'player'


def play_again():
    print('Play again?')
    return input().lower().startswith('y')


def make_move(board, letter, move):
    board[move] = letter


def is_winner(board, letter):
    return ((board[1] == board[2] == board[3] == letter) or
            (board[4] == board[5] == board[6] == letter) or
            (board[7] == board[8] == board[9] == letter) or
            (board[1] == board[4] == board[7] == letter) or
            (board[2] == board[5] == board[8] == letter) or
            (board[3] == board[6] == board[9] == letter) or
            (board[1] == board[5] == board[9] == letter) or
            (board[7] == board[5] == board[3] == letter))


def get_board_copy(board):
    dupe_board = []

    for i in board:
        dupe_board.append(i)

    return dupe_board


def is_space_free(board, move):
    return board[move] == ' '


def get_player_move(board):
    move = ' '
    while move not in '1 2 3 4 5 6 7 8 9'.split() or not is_space_free(board, int(move)):
        print('Move?')
        move = input()
    return int(move)


def choose_random_move_from_list(board, moves_list):
    possible_moves = []
    for i in moves_list:
        if is_space_free(board, i):
            possible_moves.append(i)

    if len(possible_moves) > 0:
        return random.choice(possible_moves)
    else:
        return None


def get_computer_move(board, computer_letter):
    if computer_letter == 'X':
        player_letter = 'O'
    else:
        player_letter = 'X'

    # if this move wins the game for the computer
    for i in range(1, 10):
        copy = get_board_copy(board)
        if is_space_free(copy, i):
            make_move(copy, computer_letter, i)
            if is_winner(copy, computer_letter):
                return i

    # if this move wins the game for the player
    for i in range(1, 10):
        copy = get_board_copy(board)
        if is_space_free(copy, i):
            make_move(copy, player_letter, i)
            if is_winner(copy, player_letter):
                return i

    # random corner
    move = choose_random_move_from_list(board, [1, 3, 7, 9])
    if move is not None:
        return move

    # center
    if is_space_free(board, 5):
        return 5

    # random side
    move = choose_random_move_from_list(board, [2, 4, 6, 8])
    if move is not None:
        return move


def is_board_full(board):
    for i in range(1, 10):
        if is_space_free(board, i):
            return False
    return True


print('Welcome!')

while True:
    the_board = [' '] * 10

    player_letter, computer_letter = input_player_letter()

    turn = who_goes_first()
    print('The', turn, 'will go first!')
    game_is_playing = True

    while game_is_playing:
        if turn == 'player':
            draw_board(the_board)
            move = get_player_move(the_board)
            make_move(the_board, player_letter, move)
            if is_winner(the_board, player_letter):
                draw_board(the_board)
                print('YOU WIN!')
                game_is_playing = False
            elif is_board_full(the_board):
                draw_board(the_board)
                print('YOU TIE!')
                break
            else:
                turn = 'computer'
        else:
            move = get_computer_move(the_board, computer_letter)
            make_move(the_board, computer_letter, move)
            if is_winner(the_board, computer_letter):
                draw_board(the_board)
                print('YOU LOSE!')
                game_is_playing = False
            elif is_board_full(the_board):
                draw_board(the_board)
                print('YOU TIE!')
                break
            else:
                turn = 'player'

    if not play_again():
        break