python 面向对象中一些常用内建函数【getattr(), setattr(). hasattr(). delattr()...】

本文链接：https://blog.youkuaiyun.com/pytanght/article/details/20309827

本文深入探讨了Python中类与对象的特性，包括继承、实例化、属性操作及生命周期等核心概念。通过实例演示了如何使用issubclass、isinstance、getattr、setattr、hasattr、delattr以及super()函数，以及初始化和销毁方法__init__和__del__的基本用法。

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1.issubclass(sub,parent) #判断sub是否为parent的子类，是的话返回True,否则为False

>>> class P(object):
...     pass
... 
>>> class C(P):
...     pass
... 
>>> issubclass(C,P)
True

2.isinstance(ins,class) #判断ins是否为class的实例，是的话返回True,否则为False

>>> class P(object):
...     pass
... 
>>> class C(P):
...     pass
... 
>>> c1 = C()
>>> isinstance(c1,C)
True

3.getattr(), setattr(). hasattr(). delattr()

>>> class test(object):
...      def __init__(self):
...          self.flag = 100
... 
>>> newins = test()  #类的实例化
>>> hasattr(newins,'flag')  #hasattr 判断实例newins中也就是test（object)中是否有flag这个属性,有则返回True,否则False
True
>>> hasattr(newins,'test')
False
>>> getattr(newins,'flag')  #getattr 获取属性flag的值
100
>>> getattr(newins,'test','sorry to find it') #getattr 获取属性test的值，如果没有test属性，则返回第三个参数
'sorry to find it'
>>> dir(newins)  # dir()列出属性信息，可以看到实例中有flag属性
['__class__', '__delattr__', '__dict__', '__doc__', '__format__', '__getattribute__', '__hash__', '__init__', '__module__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'flag']
>>> setattr(newins,'test','hasValue') #setattr 给实例newins设置test属性，其值为hasValue
>>> getattr(newins,'test') #获取到值，返回test的值
'hasValue'
>>> dir(newins) #实例出现test属性
['__class__', '__delattr__', '__dict__', '__doc__', '__format__', '__getattribute__', '__hash__', '__init__', '__module__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'flag', 'test']
>>> delattr(newins,'test') #delattr 删除实例的test属性
>>> dir(newins)
['__class__', '__delattr__', '__dict__', '__doc__', '__format__', '__getattribute__', '__hash__', '__init__', '__module__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'flag']

4.super() # 寻找父类的信息

>>> class P(object):
...     def __init__(self):
...        print 'I am from P'
... 
>>> class C(P):
...     def __init__(self):
...       super(C,self).__init__()
...       print 'my parent is P'
... 
>>> new = C()
I am from P
my parent is P

5.__init__() ,__del()__

>>> class P(object):
...    def __init__(self):   #类的初始函数，在声明实例是自动调用该函数
...      print 'initializing...'
... 
>>> new = P()
initializing...
>>> class C(P):
...    def __del__(self):  #类的解构函数，删除实例，引用为0时，自动调用该函数
...       print 'finished'
... 
>>> new = C()
initializing...
>>> del new
finished