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__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:`RuntimeError` if the move is illegal.
"""
if player == self.last_player:
raise RuntimeError("It isn't your turn.")
row = self.top[column]
if row == 6:
raise RuntimeError("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
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