流畅的Python---第一章 Python数据模型

1.利用简单的例子来展示实现 __getitem__ __len__ 这2个特殊方法

　　定义一个字牌类

#encoding:utf-8
import  collections
Card = collections.namedtuple('Card',['rank','suit'])

class FrenchDeck:
    ranks = [str(n) for n in range(2,11)] + list('JQKA')
    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]

　　利用 namedtuple方法  得到一个字牌的对象

beer_card = Card('7', 'diamonds')
print(beer_card)       #Card(rank='7', suit='diamonds')
print(beer_card.rank)  #7
print(beer_card.suit)  #diamonds

#可以用 len() 函数来查看一叠牌有多少张：
deck = FrenchDeck()
print(len(deck))  #52