tictactoo: oo tictactoe (python)

player.py

class Player:
    def __init__(self, mark):
        # mark can be 'x' or 'o'
        self.mark = mark

    # different types of players can inherit from here, so >> pass
    def get_play(self, game):
        pass

class HumanPlayer(Player):
    def __init__(self, mark):
        super().__init__(mark)

    def get_play(self, game):
        play = 100 #hack!
        while play not in game.okay_plays():
            game.print_gameboard()
            play = int(input(' Hey! ' + self.mark +'! Your turn - be sure to choose an available spot: '))

        return play

tictactoo.py

from player import HumanPlayer

class Tictactoe:
    def __init__(self):
        self.marks = [' ' for _ in range(9)] #the _ = placeholder in python (also other things, but a placeholder in this case);
        self.winner_name = None

    def print_gameboard(self):
        count = 0
        for gameboard_row in [self.marks[i*3:(i+1)*3] for i in range(3)]:
            print('| ' + ' | '.join(gameboard_row) + ' |')
            count +- 1
            if count < 3:
                print('--------------')
            else:
                print('\n')

    @staticmethod
    def show_numboard():
        count = 0
        nboard = [[str(i) for i in range(j*3, (j+1)*3)] for j in range(3)]
        for row in nboard:
            print('| ' + ' | '.join(row) + ' |')
            count +- 1
            if count < 3:
                print('--------------')
            else:
                print('\n')

    def okay_plays(self):
        return [i for i, place in enumerate(self.marks) if place == ' ']

    def is_spot_okay(self, spot, mark):
        if self.marks[spot]==' ':
            self.marks[spot] = mark
            if self.winner(spot, mark):
                self.winner_name = mark
            return True
        return False

    def winner(self, spot, mark):
        # check spot row for winner
        spot_row = spot//3
        check_row = self.marks[spot_row*3:(spot_row+1)*3]
        if all([t == mark for t in check_row]):
            return True
        # check spot column for winner
        spot_col = spot%3
        check_col = [self.marks[spot_col+i*3] for i in range(3)]
        if all([t == mark for t in check_col]):
            return True
        # check diagonals for winner
        diag = [self.marks[i*4] for i in range(3)]
        if all([t == mark for t in diag]):
            return True
        antidiag = [self.marks[(i+1)*2] for i in range(3)]
        if all([t == mark for t in antidiag]):
            return True
        return False

def play(game, player_x, player_o):
    mark = input('Who starts? x or o?: ')
    while len(game.okay_plays()) > 0:
        print('')
        game.show_numboard()
        print('')
        if mark == 'x':
            spot = player_x.get_play(game)
        else:
            spot = player_o.get_play(game)
        if game.is_spot_okay(spot, mark):
            print('\n')
            game.print_gameboard()
            print('\n')
            if game.winner_name:
                print(f'The winner was {mark}!')
                return
            mark = 'x' if mark == 'o' else 'o'
    print('Tie!')

if __name__ == '__main__':
    player_x = HumanPlayer('x')
    player_o = HumanPlayer('o')
    ttt = Tictactoe()
    play(ttt, player_x, player_o)