python sorted key=函数

import collections
from random import choice

Card = collections.namedtuple("Card", ["rank", "suit"])

class FrenchDeck:
    ranks = [str(n) for n in range(2,11)] + list("JQKA")
    suits = "spades diamonds clubas 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]

deck = FrenchDeck()

suit_values = dict(spades=3, diamonds=1, clubas=0, hearts=2)

def spades_high(card):
    rank_value = FrenchDeck.ranks.index(card.rank)
    return rank_value * len(suit_values) + suit_values[card.suit]

for card in sorted(deck, key=spades_high):
    print card

sorted(deck, key=spades_high)详解：

deck 运行  __len__   然后循环deck 里面的值 传给spades_high 当值 sortd 会根据函数spades_high返回的值的大小进行排序