Newbie inheritance problem

[Oleg Broytmann]

On Mon, 2 Apr 2001, zzzzz wrote:
> Hi all, I have overwridden the __add__ method for a class, then built
> a class based on the above class; however, the object I'm returning is
> of the base class not the inherited class. If that doesn't make sense
> see below:
>
> class A:
>     def __init__(self,value=0.0)
>         self._value=float(value)
>     def __add__(self,other)
>         return A(self._value+other._value)
>
> class B(A):
>     pass
>
> x=B(3)
> y=B(2)
> z=x+y
>
> The way I've done it z becomes an instance of A not B!!! How do I do
> it correctly? Do I have to override all the __add__, __sub__, etc...
> methods?

    def __add__(self,other)
        return self.__class__(self._value+other._value)

Oleg.
----
     Oleg Broytmann            http://phd.pp.ru/            phd at phd.pp.ru
           Programmers don't die, they just GOSUB without RETURN.