class A(object):

    _c ="test"

    def __init__(self):
        print '__init__'
        self.x = None

    @property
    def a(self):
        print "using property to access attribute"
        if self.x is None:
            print "return value"
        else:
            print "error occured"
            raise AttributeError

    @a.setter
    def a(self,value):
        print 'setter',value
        self.x = value

    def __getattr__(self, name):
        print 'using __getattr__ to access attribute',name
        return "b"

    def __getattribute__(self, name):
        print "using __getattribute__ to access attribute",name
        return object.__getattribute__(self,name)


a1 = A()
print a1.a
print '-'*10

a1.a =1
print a1.a

print '*'*10

print a1._c

输出：

__init__
using __getattribute__ to access attribute a
using property to access attribute
using __getattribute__ to access attribute x
return value
None
----------
setter 1
using __getattribute__ to access attribute a
using property to access attribute
using __getattribute__ to access attribute x
error occured
using __getattr__ to access attribute a
b
**********
using __getattribute__ to access attribute _c
test