Detect target name in descriptor __set__ method

[DG]

On Jul 22, 6:05 pm, "Gabriel Genellina" <gagsl-... at yahoo.com.ar>
wrote:
> En Wed, 22 Jul 2009 11:01:09 -0300, Rhodri James  
> <rho... at wildebst.demon.co.uk> escribió:
>
> > On Wed, 22 Jul 2009 06:02:55 +0100, Gabriel Genellina  
> > <gagsl-... at yahoo.com.ar> wrote:
>
> >> class X(object):
> >>    foo = descriptor()
>
> >> x = X()
> >> x.foo = "value"
>
> > Isn't this going to create a brand new instance attribute x.foo that has  
> > nothing to do with the descriptor anyway?
>
> No, it's up to the descriptor __set__ method what happens in this case.  
> Think of the standard 'property' descriptor, the fset function can do  
> whatever it wants.
> Also, a data descriptor takes precedence over any instance attribute of  
> the same name that might exist.
>
> --
> Gabriel Genellin

You might've already thought of this (and it is annoying), but you
could pass the name through the descriptor's init method.  I believe
this is the only way besides assigning a metaclass that will look for
that type of descriptor upon class creation and set the descriptor's
name at that time.

class A(object):
    def __init__(self, attr_name):
        self._name = attr_name
    def __set__(self, instance, value):
        self.instance.__dict__[self._name] = value
        # or something like that...

class B(object):
    foo = A('foo')