定义:
def sorted(*args, **kwargs): # real signature unknown """ Return a new list containing all items from the iterable in ascending order. A custom key function can be supplied to customize the sort order, and the reverse flag can be set to request the result in descending order. """ pass
给它一个可迭代对象,返回一个按照升序的新的列表
用户可以自定义关键函数来实现排序,也可以设置反向标志设置为降序。
用法:
sorted(iterable, key=None, reverse=False)
key可以为自定义函数,函数只有一个参数,具体的函数的参数就是取自于可迭代对象中,指定可迭代对象中的一个元素来进行排序。
reverse 默认False,代表升序,设置为True的时候,代表降序。
代码举例一:
import collections from random import choice Card = collections.namedtuple('Card', ['rank', 'suit']) class FrenchDeck: ranks = [str(n) for n in range(3, 11)] + list("JQKA2") suits = 'spades dimonds clubs hearts'.split(" ") def __init__(self): self._cards = [Card(rank, suit) for rank in self.ranks for suit in self.suits] def __len__(self): return len(self._cards) def __getitem__(self, position): return self._cards[position] deck = FrenchDeck() suit_values = dict(spades=3, dimonds=2, clubs=1, hearts=0) def spades_high(card): rank_value = FrenchDeck.ranks.index(card.rank) return rank_value * 4 + suit_values[card.suit] for card in sorted(deck, key=spades_high): print(card)
代码中,deck是个可迭代对象,deck打印出如下
Card(rank='3', suit='spades') Card(rank='3', suit='dimonds') Card(rank='3', suit='clubs') Card(rank='3', suit='hearts') Card(rank='4', suit='spades') Card(rank='4', suit='dimonds') Card(rank='4', suit='clubs') Card(rank='4', suit='hearts') Card(rank='5', suit='spades') Card(rank='5', suit='dimonds') Card(rank='5', suit='clubs') Card(rank='5', suit='hearts') Card(rank='6', suit='spades') Card(rank='6', suit='dimonds') Card(rank='6', suit='clubs') Card(rank='6', suit='hearts') Card(rank='7', suit='spades') Card(rank='7', suit='dimonds') Card(rank='7', suit='clubs') Card(rank='7', suit='hearts') Card(rank='8', suit='spades') Card(rank='8', suit='dimonds') Card(rank='8', suit='clubs') Card(rank='8', suit='hearts') Card(rank='9', suit='spades') Card(rank='9', suit='dimonds') Card(rank='9', suit='clubs') Card(rank='9', suit='hearts') Card(rank='10', suit='spades') Card(rank='10', suit='dimonds') Card(rank='10', suit='clubs') Card(rank='10', suit='hearts') Card(rank='J', suit='spades') Card(rank='J', suit='dimonds') Card(rank='J', suit='clubs') Card(rank='J', suit='hearts') Card(rank='Q', suit='spades') Card(rank='Q', suit='dimonds') Card(rank='Q', suit='clubs') Card(rank='Q', suit='hearts') Card(rank='K', suit='spades') Card(rank='K', suit='dimonds') Card(rank='K', suit='clubs') Card(rank='K', suit='hearts') Card(rank='A', suit='spades') Card(rank='A', suit='dimonds') Card(rank='A', suit='clubs') Card(rank='A', suit='hearts') Card(rank='2', suit='spades') Card(rank='2', suit='dimonds') Card(rank='2', suit='clubs') Card(rank='2', suit='hearts')
spades_high是自定义函数,此函数参数取自于可迭代对象deck中,此处为deck中52个由namedtuple
创建的名叫Card的元祖对象,通过对spades_high函数的输出数值进行升序排序。
最后排序之后的输出如下:
Card(rank='3', suit='hearts') Card(rank='3', suit='clubs') Card(rank='3', suit='dimonds') Card(rank='3', suit='spades') Card(rank='4', suit='hearts') Card(rank='4', suit='clubs') Card(rank='4', suit='dimonds') Card(rank='4', suit='spades') Card(rank='5', suit='hearts') Card(rank='5', suit='clubs') Card(rank='5', suit='dimonds') Card(rank='5', suit='spades') Card(rank='6', suit='hearts') Card(rank='6', suit='clubs') Card(rank='6', suit='dimonds') Card(rank='6', suit='spades') Card(rank='7', suit='hearts') Card(rank='7', suit='clubs') Card(rank='7', suit='dimonds') Card(rank='7', suit='spades') Card(rank='8', suit='hearts') Card(rank='8', suit='clubs') Card(rank='8', suit='dimonds') Card(rank='8', suit='spades') Card(rank='9', suit='hearts') Card(rank='9', suit='clubs') Card(rank='9', suit='dimonds') Card(rank='9', suit='spades') Card(rank='10', suit='hearts') Card(rank='10', suit='clubs') Card(rank='10', suit='dimonds') Card(rank='10', suit='spades') Card(rank='J', suit='hearts') Card(rank='J', suit='clubs') Card(rank='J', suit='dimonds') Card(rank='J', suit='spades') Card(rank='Q', suit='hearts') Card(rank='Q', suit='clubs') Card(rank='Q', suit='dimonds') Card(rank='Q', suit='spades') Card(rank='K', suit='hearts') Card(rank='K', suit='clubs') Card(rank='K', suit='dimonds') Card(rank='K', suit='spades') Card(rank='A', suit='hearts') Card(rank='A', suit='clubs') Card(rank='A', suit='dimonds') Card(rank='A', suit='spades') Card(rank='2', suit='hearts') Card(rank='2', suit='clubs') Card(rank='2', suit='dimonds') Card(rank='2', suit='spades')
代码举例二:
a = [-5, -3, -1, 0, 2, 4, 6] print(sorted(a, key=lambda x: x**2)) print(sorted(a, key=lambda x: x**2, reverse=True))
[0, -1, 2, -3, 4, -5, 6]
[6, -5, 4, -3, 2, -1, 0]
即按照lambda函数:x的平方值的升序,来对列表a排序,通过设置reverse标志,来设置升序或者降序。