《流畅的Python》第一章学习笔记
【摘要】 1.1 一摞Python风格的纸牌
Python 解释器碰到特殊的句法时，会使用特殊方法去激活一些基本的对象操作，这些特殊方法的名
字以两个下划线开头，以两个下划线结尾（例如__getitem__）。比如 obj[key] 的背后就是
__getitem__ 方法，为了能求得my_collection[key] 的值，解释器实际上会调用
my_co...
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import collections
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Card = collections.namedtuple('Card',['rank','suit']) #需要掌握命名元组的使用
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class FrenchDeck:
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ranks = [str(n) for n in range(2,11)] + list('JQKA') #13张牌
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suits = 'spades diamonds clubs hearts'.split() #4个花色
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#ranks和suits都是list类型
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def __init__(self):
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self._cards = [Card(rank,suit) for suit in self.suits
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for rank in self.ranks] #两个for循环使用技巧，需
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要掌握
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def __len__(self):
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return len(self._cards) #返回列表长度，使对象能直接嗲用len函数
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def __getitem__(self,position):
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return self._cards[position] #通过列表[下标]返回元素，从而支持getitem功能
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In [2]: beer_card = Card('7','diamonds')
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In [3]: beer_card
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Out[3]: Card(rank='7', suit='diamonds')
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In [4]: deck = FrenchDeck()
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In [5]: len(deck)
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Out[5]: 52
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In [6]: deck[0]
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Out[6]: Card(rank='2', suit='spades')
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In [7]: deck[-1]
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Out[7]: Card(rank='A', suit='hearts')
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In [9]: choice(deck)
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Out[9]: Card(rank='5', suit='hearts')
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In [10]: choice(deck)
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Out[10]: Card(rank='9', suit='spades')
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In [11]: choice(deck)
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Out[11]: Card(rank='7', suit='hearts')
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In [12]: deck[:3]
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Out[12]:
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[Card(rank='2', suit='spades'),
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Card(rank='3', suit='spades'),
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Card(rank='4', suit='spades')]
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In [13]: deck[12:13]
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Out[13]: [Card(rank='A', suit='spades')]
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In [14]: deck[12::13]
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Out[14]:
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[Card(rank='A', suit='spades'),
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Card(rank='A', suit='diamonds'),
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Card(rank='A', suit='clubs'),
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Card(rank='A', suit='hearts')]
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In [16]: for card in deck: #doctest: +ELLIPSIS
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...: print (card)
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...:
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Card(rank='2', suit='spades')
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Card(rank='3', suit='spades')
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Card(rank='4', suit='spades')
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Card(rank='5', suit='spades')
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Card(rank='6', suit='spades')
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Card(rank='7', suit='spades')
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Card(rank='8', suit='spades')
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Card(rank='9', suit='spades')
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.....
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In [17]: for card in reversed(deck):#doctest:+ELLIPSIS
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...: print (card)
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...:
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Card(rank='A', suit='hearts')
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Card(rank='K', suit='hearts')
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Card(rank='Q', suit='hearts')
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Card(rank='J', suit='hearts')
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Card(rank='10', suit='hearts')
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Card(rank='9', suit='hearts')
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Card(rank='8', suit='hearts')
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Card(rank='7', suit='hearts')
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.......
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In [19]: Card('Q','hearts') in deck
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Out[19]: True
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In [20]: Card('7','beass') in deck
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Out[20]: False
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suit_values = dict(spades=3, hearts=2, diamonds=1, clubs=0)
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def spades_high(card):
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rank_value = FrenchDeck.ranks.index(card.rank) #rank_value，'2' 的值为0，'A'的值为12
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return rank_value * len(suit_values) + suit_values[card.suit]
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>>> for card in sorted(deck, key=spades_high): # doctest: +ELLIPSIS
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... print(card)
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Card(rank='2', suit='clubs')
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Card(rank='2', suit='diamonds')
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Card(rank='2', suit='hearts')
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... (46 cards ommitted)
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Card(rank='A', suit='diamonds')
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Card(rank='A', suit='hearts')
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Card(rank='A', suit='spades')
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from math import hypot
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class Vector:
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def __init__(self,x=0,y=0):
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self.x = x
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self.y = y
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def __repr__(self):
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return 'Vector(%r,%r)' % (self.x,self.y)
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def __abs__(self):
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return hypot(self.x,self.y)
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def __bool__(self):
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return bool(abs(self))
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def __add__(self,other):
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x = self.x + other.x
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y = self.y + other.y
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return Vector(x,y)
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def __mul__(self,scalar):
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return Vector(self.x * scalar,self.y * scalar)
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>>> vect = Vector(3,4)
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>>> vect #这里调用了__repr__函数，如果类中没有定义这个函数，这打印类似这
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样的值<Vector object at 0x10e100070>
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Vector(3,4)
文章来源: blog.csdn.net，作者：悦来客栈的老板，版权归原作者所有，如需转载，请联系作者。
原文链接：blog.csdn.net/qq523176585/article/details/78538957
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