getattr()
Docstring: getattr(object, name[, default]) -> value Get a named attribute from an object;
getattr(x, ‘y‘) is equivalent to x.y. When a default argument is given, it is returned when the attribute doesn‘t exist; without it, an exception is raised in that case.
setattr()
Signature: setattr(obj, name, value, /)
Docstring: Sets the named attribute on the given object to the specified value.
setattr(x, ‘y‘, v) is equivalent to ``x.y = v‘‘
delattr()
Signature: delattr(obj, name, /)
Docstring: Deletes the named attribute from the given object.
delattr(x, ‘y‘) is equivalent to ``del x.y‘‘
避免内置函数的递归调用：
1 class rectan(): 2 def __init__(self, x, y): 3 self.x = x 4 self.y = y 5 6 def __setattr__(self, name, value): 7 print(‘setattr‘) 8 if name == ‘square‘: 9 self.x = vlaue 10 self.y = value 11 12 # super().__setattr__(‘x‘, value) 13 # super().__setattr__(‘y‘, value) 14 else: 15 # self.name = value 16 super().__setattr__(name, value)
如使用第15 行进行赋值操作会出现递归现象，这是由于，在实例化对象时，调用了 __init__()方法， 而该方法中进行了 属性设置操作，对于该对象来说就需要调用该对象的__setattr__()方法进行属性设置，而15行的属性设置仍然需要调用该对象本身的__setattr__()方法，从而产生递归调用，解决办法是使用 16行代码，使用其他对象的__setattr__()方法，由于父类与该对象有直接关系，因此调用父类的方法。
属性名以字符串的方式传入。
__getattr__(self, name):定义当试图访问一个不存在的属性名时的行为。(基类object 中无该方法)
__getattribute__(self, name)：定义该类的属性被访问时的行为。 属性被访问时先访问的方法
__setattr__(self, name, value):定义一个属性被设置时的行为
__delattr__(self, name): 定义一个属性被删除时的行为
1 class test(): 2 def __setattr__(self, name, value): 3 print(‘setattr‘) 4 super().__setattr__(name, value) 5 6 def __getattr__(self,name): 7 print(‘setattr‘) 8 9 10 def __getattribute__(self, name): 11 print(‘getattribute‘) 12 return super().__getattribute__(name) 13 14 def __delattr__(self, name): 15 print(‘delsttr‘) 16 super().__delattr__(name) 17 18 t = test() 19 setattr(t,‘x‘,10) 20 getattr(t,‘x‘) 21 delattr(t,‘x‘) 22 getattr(t,‘x‘) 23 24 ################################ 25 26 setattr 27 getattribute 28 delsttr 29 getattribute 30 setatt
原文：https://www.cnblogs.com/JYNNO1/p/10479738.html