class A(object):
def __init__(self):
self.A = "aa"
self.C = "CC"
del self.C

def __setattr__(self,name,value):
‘‘‘
@summary: 每当属性被赋值的时候都会调用该方法，因此不能再该方法内赋值 self.name = value 会死循环
‘‘‘
print "__setattr__:Set %s Value %s"%(name,value)
self.__dict__[name] = value

def __getattr__(self,name):
‘‘‘
@summary: 当访问不存在的属性时会调用该方法
‘‘‘
print "__getattr__:No attribute named ‘%s‘"%name
return None

def __delattr__(self,name):
‘‘‘
@summary: 当删除属性时调用该方法
‘‘‘
print "__delattr__:Delect attribute ‘%s‘"%name
del self.__dict__[name]
print self.__dict__

if __name__ == "__main__":
X = A()
a = X.aa
输出：
__setattr__:Set A Value aa
__setattr__:Set C Value CC
__delattr__:Delect attribute ‘C‘
{‘A‘: ‘aa‘}
__getattr__:No attribute named ‘aa‘