content: __all__ = ["PLAYER1", "PLAYER2", "Connect4"]
  
  PLAYER1, PLAYER2 = "red", "yellow"
  
  
  class Connect4:
      """
      A Connect Four game.
  
      Play moves with :meth:`play`.
  
      Get past moves with :attr:`moves`.
  
      Check for a victory with :attr:`winner`.
  
      """
  
      def __init__(self):
          self.moves = []
          self.top = [0 for _ in range(7)]
          self.winner = None
  
      @property
      def last_player(self):
          """
          Player who played the last move.
  
          """
          return PLAYER1 if len(self.moves) % 2 else PLAYER2
  
      @property
      def last_player_won(self):
          """
          Whether the last move is winning.
  
          """
          b = sum(1 << (8 * column + row) for _, column, row in self.moves[::-2])
          return any(b & b >> v & b >> 2 * v & b >> 3 * v for v in [1, 7, 8, 9])
  
      def play(self, player, column):
          """
          Play a move in a column.
  
          Returns the row where the checker lands.
  
          Raises :exc:`ValueError` if the move is illegal.
  
          """
          if player == self.last_player:
              raise ValueError("It isn't your turn.")
  
          row = self.top[column]
          if row == 6:
              raise ValueError("This slot is full.")
  
          self.moves.append((player, column, row))
          self.top[column] += 1
  
          if self.winner is None and self.last_player_won:
              self.winner = self.last_player
  
          return row
  