n = 1

while True:
    if n%2 == 0:
        player_mark = 'O'
    else:
        player_mark = 'X'

    game_display(row1, row2, row3)
    
    turn = input('Enter position (Player {}) : '.format(player_mark))
    print()
    row_number = int(turn[1])
    column_number = int(turn[2])-1

    if row_number == 1:
        position = row1[column_number]
        if position == ' ':
            row1[column_number] = player_mark
                
        else:
            pass

    elif row_number == 2:
        position = row2[column_number]
        if position == ' ':
            row2[column_number] = player_mark
                
        else:
            pass

    elif row_number == 3:
        position = row3[column_number]
        if position == ' ':
            row3[column_number] = player_mark
                
        else:
            pass