def input_player_letter():
    '''Ask the player which letter they want to be;
       returns a list with the player's letter as first iem and the
       computer's letter as the second item.
    '''
    letter = ''
    while ('X', 'O') not in letter:
        letter = input('Do you want to be X or O?\n').upper()

    if letter == 'X':
        return ['X', 'O']
    else:
        return ['O', 'X']
dataset/ETHPy150Open aroberge/pyproj/iwip/tictactoe_mod.py/input_player_letter/swapped operands of `not in`