python之路----面向对象进阶二

item系列

__getitem__\__setitem__\__delitem__

class Foo:
    def __init__(self,name,age,sex):
        self.name = name
        self.age = age
        self.sex = sex

    def __getitem__(self, item):
        if hasattr(self,item):
            return self.__dict__[item]

    def __setitem__(self, key, value):
        self.__dict__[key] = value

    def __delitem__(self, key):
        del self.__dict__[key]

f = Foo('egon',38,'男')
print(f['name'])
f['hobby'] = '男'
print(f.hobby,f['hobby'])
del f.hobby      # object 原生支持  __delattr__
del f['hobby']   # 通过自己实现的
print(f.__dict__)

__new__

class A:
    def __init__(self):
        self.x = 1
        print('in init function')
    def __new__(cls, *args, **kwargs):
        print('in new function')
        return object.__new__(A, *args, **kwargs)

a = A()
print(a.x)

 单例模式：

class Singleton:
    def __new__(cls, *args, **kw):
        if not hasattr(cls, '_instance'):
            cls._instance = object.__new__(cls, *args, **kw)
        return cls._instance

one = Singleton()
two = Singleton()

two.a = 3
print(one.a)
# 3
# one和two完全相同,可以用id(), ==, is检测
print(id(one))
# 29097904
print(id(two))
# 29097904
print(one == two)
# True
print(one is two)

一个类 始终 只有 一个 实例
# 当你第一次实例化这个类的时候 就创建一个实例化的对象
# 当你之后再来实例化的时候 就用之前创建的对象

__call__

对象后面加括号，触发执行。

注：构造方法的执行是由创建对象触发的，即：对象 = 类名() ；而对于 __call__ 方法的执行是由对象后加括号触发的，即：对象() 或者 类()()

class Foo:

    def __init__(self):
        pass
    
    def __call__(self, *args, **kwargs):

        print('__call__')


obj = Foo() # 执行 __init__
obj()       # 执行 __call__ 

__len__

class A:
    def __init__(self):
        self.a = 1
        self.b = 2

    def __len__(self):
        return len(self.__dict__)
a = A()
print(len(a))

__eq__

class A:
    def __init__(self):
        self.a = 1
        self.b = 2

    def __eq__(self,obj):
        if  self.a == obj.a and self.b == obj.b:
            return True
a = A()
b = A()
print(a == b)

 

class FranchDeck:
    ranks = [str(n) for n in range(2,11)] + list('JQKA')
    suits = ['红心','方板','梅花','黑桃']

    def __init__(self):
        self._cards = [Card(rank,suit) for rank in FranchDeck.ranks
                                        for suit in FranchDeck.suits]

    def __len__(self):
        return len(self._cards)

    def __getitem__(self, item):
        return self._cards[item]

deck = FranchDeck()
print(deck[0])
from random import choice
print(choice(deck))
print(choice(deck))

纸牌游戏

class FranchDeck:
    ranks = [str(n) for n in range(2,11)] + list('JQKA')
    suits = ['红心','方板','梅花','黑桃']

    def __init__(self):
        self._cards = [Card(rank,suit) for rank in FranchDeck.ranks
                                        for suit in FranchDeck.suits]

    def __len__(self):
        return len(self._cards)

    def __getitem__(self, item):
        return self._cards[item]

    def __setitem__(self, key, value):
        self._cards[key] = value

deck = FranchDeck()
print(deck[0])
from random import choice
print(choice(deck))
print(choice(deck))

from random import shuffle
shuffle(deck)
print(deck[:5])

class Person:
    def __init__(self,name,age,sex):
        self.name = name
        self.age = age
        self.sex = sex

    def __hash__(self):
        return hash(self.name+self.sex)

    def __eq__(self, other):
        if self.name == other.name and self.sex == other.sex:return True


p_lst = []
for i in range(84):
    p_lst.append(Person('egon',i,'male'))

print(p_lst)
print(set(p_lst))