您可以定义一个可以抛出的自定义异常，然后将对game的调用 Package 在try-catch中，并在其后提示检查用户是否愿意再次播放。
定义例外：

class StopGameIteration(Exception):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

重写game()函数以使用异常：

def game():

  def first_check():
    player_sum = sum(player)
    dealer_sum = sum(dealer)
    if 21 in [player_sum,dealer_sum]:
      if 21 in [player_sum] and 21 in [dealer_sum]:
        print("Both you and the dealer have Blackjack, its a push!!")
      blackjack()
      raise StopGameIteration("Had blackjack")

并将调用封装在try catch中：

while True:
  try: 
    game()
  except StopGameIteration:
    pass

  if "n" in input("Do you want to play again? Y or N").lower():
    break

您甚至可以创建几个异常，以便根据中断函数的原因调整行为：

class GameException(Exception):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

class BlackjackAchieved(GameException):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

class PlayerCheated(GameException):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

然后做出相应的React：

while True:
  try: 
    game()
  except BlackjackAchieved:
    print("Someone got a blackjack")
  except PlayerCheated:
    print("oh no, someone cheated")
  except GameException:
    print("Something related to the game happened to cause it to quit")

  if "n" in input("Do you want to play again? Y or N").lower():
    break

编辑：@pranav-hosangadi说得很对：try-catch应该在game函数内部，这样游戏的逻辑就完全独立了，然后，在try-catch块的finally子句中，可以选择使用return返回到外部循环。