import collections
Card=collections.namedtuple('Card',['rank','suit'])
class FrenchDeck:
ranks = [str(n) for n in range(2,11)] + list('JKQA')
suits = 'spades diamonds clubs hearts'.split( )
def __init__(self):
self._cards = [Card(rank,suit) for suit in self.suits
for rank in self.ranks]
def __len__(self):
return len(self._cards)
def __getitem__(self,position):
return self._cards[position]
为什么用len()显示TypeError: object of type 'FrenchDeck' has no len()