《流畅的python》 1.1笔记

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]

suit_values = dict(spades=3, hearts=2, diamonds=1, clubs=0)
def spades_high(card):
    rank_value = FrenchDeck.ranks.index(card.rank) #index返回参数在对象中第一次出现的位置
    return rank_value * len(suit_values) + suit_values[card.suit]

deck = FrenchDeck()

len(deck)
deck.__len__()
FrenchDeck.__len__(deck)
#All these forms are avaible,编译器会将这三种表达方式都解释为同一指令

for card in deck: #由于定义了__getitem__方法，所以FrenchDeck类的所有对象都是可迭代的
    pass

for card in sorted(deck):
    print(card)

__contains__方法和 in 息息相关，举例

>>> str1 = "abcdefg"
>>> str2 = "bcd"
>>> val = str1.__contains__(str2)
>>> val
True

 只要一个对象是可迭代的，即使它没有__contains__属性，in可以以循环的方式在该对象中搜寻。

如果一个对象拥有了__getitem__属性，那么它可以被搜寻，被迭代。