《流畅的Python》第一章学习笔记

      import collections
      Card = collections.namedtuple('Card',['rank','suit'])  #需要掌握命名元组的使用
      class FrenchDeck:
       ranks = [str(n) for n in range(2,11)] + list('JQKA')  #13张牌
       suits = 'spades diamonds clubs hearts'.split() #4个花色
      #ranks和suits都是list类型
      def __init__(self):
       self._cards = [Card(rank,suit) for suit in self.suits
      for rank in self.ranks]  #两个for循环使用技巧，需
      要掌握
      def __len__(self):
      return len(self._cards)   #返回列表长度，使对象能直接嗲用len函数
      def __getitem__(self,position):
      return self._cards[position] #通过列表[下标]返回元素，从而支持getitem功能
  
 

      In [2]: beer_card = Card('7','diamonds')
      In [3]: beer_card
      Out[3]: Card(rank='7', suit='diamonds')
  
 

      In [4]: deck = FrenchDeck()
      In [5]: len(deck)
      Out[5]: 52
  
 

      In [6]: deck[0]
      Out[6]: Card(rank='2', suit='spades')
      In [7]: deck[-1]
      Out[7]: Card(rank='A', suit='hearts')
  
 

      In [9]: choice(deck)
      Out[9]: Card(rank='5', suit='hearts')
      In [10]: choice(deck)
      Out[10]: Card(rank='9', suit='spades')
      In [11]: choice(deck)
      Out[11]: Card(rank='7', suit='hearts')
  
 

      In [12]: deck[:3]
      Out[12]:
      [Card(rank='2', suit='spades'),
       Card(rank='3', suit='spades'),
       Card(rank='4', suit='spades')]
      In [13]: deck[12:13]
      Out[13]: [Card(rank='A', suit='spades')]
      In [14]: deck[12::13]
      Out[14]:
      [Card(rank='A', suit='spades'),
       Card(rank='A', suit='diamonds'),
       Card(rank='A', suit='clubs'),
       Card(rank='A', suit='hearts')]
  
 

      In [16]: for card in deck: #doctest: +ELLIPSIS
       ...: print (card)
       ...:
      Card(rank='2', suit='spades')
      Card(rank='3', suit='spades')
      Card(rank='4', suit='spades')
      Card(rank='5', suit='spades')
      Card(rank='6', suit='spades')
      Card(rank='7', suit='spades')
      Card(rank='8', suit='spades')
      Card(rank='9', suit='spades')
      .....
  
 

      In [17]: for card in reversed(deck):#doctest:+ELLIPSIS
       ...: print (card)
       ...:
      Card(rank='A', suit='hearts')
      Card(rank='K', suit='hearts')
      Card(rank='Q', suit='hearts')
      Card(rank='J', suit='hearts')
      Card(rank='10', suit='hearts')
      Card(rank='9', suit='hearts')
      Card(rank='8', suit='hearts')
      Card(rank='7', suit='hearts')
      .......
  
 

      In [19]: Card('Q','hearts') in deck
      Out[19]: True
      In [20]: Card('7','beass') in deck
      Out[20]: False
  
 

      suit_values = dict(spades=3, hearts=2, diamonds=1, clubs=0)
      def spades_high(card):
      rank_value = FrenchDeck.ranks.index(card.rank) #rank_value，'2' 的值为0，'A'的值为12
      return rank_value * len(suit_values) + suit_values[card.suit]
  
 

      >>> for card in sorted(deck, key=spades_high): # doctest: +ELLIPSIS
      ... print(card)
      Card(rank='2', suit='clubs')
      Card(rank='2', suit='diamonds')
      Card(rank='2', suit='hearts')
      ... (46 cards ommitted)
      Card(rank='A', suit='diamonds')
      Card(rank='A', suit='hearts')
      Card(rank='A', suit='spades')
  
 

      from math import hypot
      class Vector:
      def __init__(self,x=0,y=0):
       self.x = x
       self.y = y
      def __repr__(self):
      return 'Vector(%r,%r)' % (self.x,self.y)
      def __abs__(self):
      return hypot(self.x,self.y)
      def __bool__(self):
      return bool(abs(self))
      def __add__(self,other):
       x = self.x + other.x
       y = self.y + other.y
      return Vector(x,y)
      def __mul__(self,scalar):
      return Vector(self.x * scalar,self.y * scalar)
  
 

      >>> vect = Vector(3,4)
      >>> 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
      样的值<Vector object at 0x10e100070>
      Vector(3,4)
  
 

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原文链接：blog.csdn.net/qq523176585/article/details/78538957