inheritance

[Duncan Booth]

"Sean Ross" <frobozz_electric at hotmail.com> wrote in 
news:bca8di$e84$1 at driftwood.ccs.carleton.ca:

> class Base:
>     def __init__(self, value):
>         self.value = value
>     def __mul__(self, other):
>         return self.__class__(self.value * other.value)
> 
> class Child(Base):
>     def __init__(self, value):
>         Base.__init__(self, value)
> 
> x = Base(2)
> y = Base(3)
> z = Child(4)
> w = Child(5)
> print x*y
> print z*w
> 
> """OUTPUT
><__main__.Base instance at 0x009991E0>
><__main__.Child instance at 0x009991E0>
> """

But:
>>> x*z
<__main__.Base instance at 0x009392A0>
>>> z*x
<__main__.Child instance at 0x00934520>

For consistency you may need to base the type on both self and other.

e.g.
class Base:
    def __init__(self, value):
        self.value = value
    def __mul__(self, other):
        if issubclass(self.__class__, other.__class__):
            resType = self.__class__
        else:
            resType = other.__class__
        return resType(self.value * other.value)

-- 
Duncan Booth                                             duncan at rcp.co.uk
int month(char *p){return(124864/((p[0]+p[1]-p[2]&0x1f)+1)%12)["\5\x8\3"
"\6\7\xb\1\x9\xa\2\0\4"];} // Who said my code was obscure?