python property

property Found at: __builtin__
property(fget=None, fset=None, fdel=None, doc=None) -> property attribute

fget is a function to be used for getting an attribute value, and likewise
fset is a function for setting, and fdel a function for del'ing, an
attribute. Typical use is to define a managed attribute x:
class C(object):
def getx(self): return self.__x
def setx(self, value): self.__x = value
def delx(self): del self.__x
x = property(getx, setx, delx, "I'm the 'x' property.")

class SessionMixin(object):
    def __init__(self):
        self._x = 'init'
        
    def getx(self):
        print 'getx',
        return self._x
    
    def setx(self, value):
        print 'setx'
        self._x = value
        
    def delx(self):
        print 'delx'
        del self._x
    
    x = property(getx, setx, delx, "I'm the 'x' property.")

test = SessionMixin()

test.x = 'value'
print test.x
del test.x

输出：

setx
getx value
delx