Improvement of http://stackoverflow.com/questions/41388923/tictactoe-tie-error

tictactoe.py

#!/usr/bin/env python
"""Tic Tac Toe game."""

PLAYER1 = True
BOARD = [[1, 2, 3],
         [4, 5, 6],
         [7, 8, 9]]


def show(board):
    """Print the current board state."""
    print
    for i, row in enumerate(board):
        print ' {0} | {1} | {2} '.format(*row)
        if i != len(board) - 1:
            print '-' * 11
    print


def check_win(board):
    """Return winning player mark or None."""
    rotated_board = zip(*board)  # matrix rotate rows to cols

    # check rows and cols
    for board_rotation in (board, rotated_board):
        for row in board_rotation:
            if (not isinstance(row[0], int) and
                    row.count(row[0]) == len(row)):
                return row[0]

    # check diags
    if (not isinstance(board[1][1], int) and
        (board[0][0] == board[1][1] == board[2][2] or
         board[2][0] == board[1][1] == board[0][2])):
        return board[1][1]


def board_full(board):
    """Return True if no moves left."""
    for row in board:
        if True in [isinstance(v, int) for v in row]:
            return False
    return True


if __name__ == '__main__':
    print 'Welcome to a two-player Tic.Tac.Toe Game!'
    print "Just pick a spot to put your mark!"
    print 'Now, start!'
    show(BOARD)

    while check_win(BOARD) is None and not board_full(BOARD):
        try:
            move = int(input('Player {0}, select a spot (1-9): '.format(
                1 if PLAYER1 else 2)))
            row = (move - 1) / 3
            col = (move - 1) % 3
            spot = BOARD[row][col]

            if isinstance(spot, int):
                BOARD[row][col] = 'X' if PLAYER1 else 'O'
                PLAYER1 = not PLAYER1
            else:
                print 'This spot is taken.'

        except (ValueError, IndexError):
            print 'Please enter a number from 1 to 9.'

        show(BOARD)

    winner = check_win(BOARD)
    if winner:
        print 'Player {0} won!'.format(1 if winner == 'X' else 2)
    else:
        print "It's a tie."