Create an alias to an attribute on superclass

[Sean DiZazzo]

On Thursday, February 1, 2018 at 10:37:32 AM UTC-8, Chris Angelico wrote:
> On Fri, Feb 2, 2018 at 5:22 AM, Sean DiZazzo <sean.dizazzo at gmail.com> wrote:
> > Hi!
> >
> > I basically just want to create an alias to an attribute on an item's superclass.  So that after I create the subclass object, I can access the alias attribute to get the value back.
> >
> > <pre>
> > class Superclass(object):
> >     def __init__(self, value):
> >         """
> >             I want to pass x by reference, so that any time
> >             x on the subclass is updated, so is the alias here
> >         """
> >         self.alias = value
> >
> > class Subclass(Superclass):
> >     def __init__(self, x):
> >         self.x = x
> >         Superclass.__init__(self, self.x)
> >
> >     def __repr__(self):
> >         return "x: %s\nalias: %s" % (self.x, self.alias)
> >
> >
> > if __name__ == "__main__":
> >     foo = Subclass(1)
> >     print foo.alias
> >
> >     foo.x = 6
> >     # Should return 6 !!!
> >     print foo.alias
> >
> > </pre>
> 
> ISTM the easiest way would be to define a property on the superclass:
> 
> class Superclass(object):
>     @property
>     def alias(self):
>         return self.x
> 
> Whatever happens, self.alias will be identical to self.x. Is that what
> you're after?
> 
> ChrisA

Yes, but that doesn't seem to work.  It looks like there is a way to do it if you make the original value a list (mutable) instead of an integer.  I really need to do it with an arbitrary object.  Not sure if I can hack the list trick to work in my case though.