Overriding a global

[Joshua Landau]

On 13 December 2011 19:54, Ian Kelly <ian.g.kelly at gmail.com> wrote:

> On Tue, Dec 13, 2011 at 12:43 PM, Joshua Landau
> <joshua.landau.ws at gmail.com> wrote:
> > On 13 December 2011 19:34, Ian Kelly <ian.g.kelly at gmail.com> wrote:
> >>
> >> On Tue, Dec 13, 2011 at 1:34 AM, Joshua Landau
> >> <joshua.landau.ws at gmail.com> wrote:
> >> >> No, there is another difference, the reason for rebinding the name.
> >> >> In a subclass, you would rebind a class attribute because that
> >> >> particular attribute, which you need to change, is used and expected
> >> >> by external code, either in the base class or in code that uses its
> >> >> API (or both).  Local variables in functions, on the other hand, are
> >> >> not externally visible, so there is no need to do this in order to
> >> >> conform to the expectations of external code.  All it does in that
> >> >> case is to sow potential confusion.
> >> >>
> >> > So you're saying you should never extend methods or attributes that
> >> > aren't meant to be used as part of of the API? Because I can claim
> >> > guilty on this point.
> >>
> >> No, I'm only saying that replacing attributes in subclasses is
> >> accepted because it is necessary due to external dependencies, and
> >> that local variables in functions don't have that excuse.
> >
> >
> > But they aren't needed due to external dependencies if they're
> > implementation-specific and not part of the API, no?
>
> By "external dependencies" I mean anything that's not specifically
> part of the subclass.  This includes the base class.  If they're not
> part of the API, then the base class presumably uses them for
> something, and by replacing them, you change the behavior of that base
> functionality.  That's an external dependency.
>

Touché. On this point, I yield.
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