python 特殊方法实例

import collections
from random import choice

card = collections.namedtuple('Card',['rank','suit']) #构建一个命名元组

class FrenchDeck:
    ranks = [str(n) for n in range(2,11)] + list('JQKA')  # 创建所有纸牌数A-K
    suit = '黑桃 方块 梅花 红心'.split()   # 创建不同的纸牌花色

    def __init__(self):
        self._cards = [Card(ranks,suit) for suit in self.suits for rank in self.ranks]  # 初始化整套扑克
    
    def __len__(self):
        return len(self._cards) # 获取整套牌的个数

    def __getitem__(self,position): 
        return self._cards[position]   # 获取特定纸牌

deck = FrenchDeck() # 实例化类
print(len(deck)) # 获取整套牌的数量 52
print(deck[0]) # 获取第一张牌  Card(rank='2',suit='黑桃')
choice(deck) # 随机选取其中某张牌 Card(rank='3',suit='梅花') Card(rank='5',suit='红心')


#排序
suit_values = dict(黑桃 = 3,方块 = 2,梅花 = 1,红心 = 0) # 定义一个字典保存不同花色对应的权重值

def spades_high(card): # 定义升序函数
    rank_value = FrenchDeck.ranks.index(card.rank) # 找到数字的索引值
    return rank_value * len(suit_values) + suit_values[card.suit] # 返回索引值*4 +对应的权重值

# 对所有卡牌进行排序
for card in sorted(deck,key = spades_high):
    print(card)

模拟数值类型

from math import hypot  

class Vector(object):
    """docstring for Vector"""
    def __init__(self, x = 0,y = 0):
        self.x= x
        self.y = y

    def __repr__(self): #得到对象的字符串表现形式
        return "Vector(%r,%r)" % (self.x,self.y)

    def __abs__(self): #用来计算向量的模
        return hypot(self.x,self.y)

    def __bool__(self): # 判断向量实例的布尔值
        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)