Question

So I have the following code, I am trying to add some sort of metadata I suppose to an attribute of a class. My idea was that I would have a getter/setter in which the getter would return a float/int/string private variable but return some extra data with it, such as a verbose name.

This works perfectly until I use the setter, which once used seems to ignore the setter and getter.

Does anyone know why what I am doing is not working? Or if there is a better way to go about what I am trying to do?

Many thanks!

class Param(float):
    def __new__(self,name,value):
        return float.__new__(self,value)

    def __init__(self,name,value):
        self.__name = name

    name = property(lambda self: self.__name)


class Beer:
    def __init__(self, temp):
        self.__T = temp

    @property
    def temp(self):
        return Param('Beer Temperature', self.__T)

    @temp.setter
    def temp(self,value):
        self.__T = float(value) 


print b.temp.name, b.temp.__class__

print b.temp * 4.5

print b.temp.name, b.temp.__class__

b.temp = 101

print b.temp.name, b.temp.__class__

Answer 1

In python 2, properties work properly only with new-style classes (derived from object):

class Beer(object):
    def __init__(self, temp):
        self.__T = temp

    @property
    def temp(self):
        return Param('Beer Temperature', self.__T)

    @temp.setter
    def temp(self,value):
        self.__T = float(value)