【Python】【fromxieyiToChouxiangjilei】

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class Vector2d:
    typecode = ‘d‘

    def __init__(self,x,y):
        self.__x = float(x)
        self.__y = float(y)
    @property
    def x(self):
        return self.__x
    @property
    def y(self):
        return self.__y
    def __iter__(self):
        return (i for i in (self.x,self.y))
from random import shuffle

l = list(range(10))
shuffle(l)
print(l)   #[1, 7, 0, 8, 5, 2, 9, 4, 6, 3]
tuple1 = (1,2)
#shuffle(tuple1)
‘‘‘
Traceback (most recent call last):
  File "C:/Users/wangxue1/PycharmProjects/fluentPython/fromxieyiToChouxiangjilei/__init__22.py", line 21, in <module>
    shuffle(tuple1)
  File "C:\Python36\lib\random.py", line 274, in shuffle
    x[i], x[j] = x[j], x[i]
TypeError: ‘tuple‘ object does not support item assignmen
‘‘‘
#这个错误信息相当明确。问题原因是，shuffle函数要调换集合中元素的位置，而tuple只实现了不尅版序列协议。可变的序列还必须提供__setitem__方法。
#Python是动态语言，因此我们可以在运行时修正这个问题，甚至还可以在交互式控制台中，
#栗子11-6 为FrenchDeck打猴子补丁（运行时修改，不改源码），把他变成可变的，让random.shuffle函数能处理
from random import shuffle
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 rank in self.ranks for suit in self.suits]
    def __len__(self):
        return len(self._cards)
    def __getitem__(self, item):
        return self._cards[item]

def set_card(deck,position,card):
    deck._cards[position] = card

FrenchDeck.__setitem__ = set_card
deck = FrenchDeck()
shuffle(deck)
print(deck[:5])

【Python】【fromxieyiToChouxiangjilei】

标签：语言   ret   print   support   line   project   collect   file   动态语言   

原文地址：http://www.cnblogs.com/suren2017/p/7662418.html