[Python-Dev] PEP 246, redux

[Carlos Ribeiro]

On Wed, 12 Jan 2005 16:07:37 -0600, Ian Bicking <ianb at colorstudy.com> wrote:
> As I think these things through, I'm realizing that registered
> adaptators really should be 100% accurate (i.e., no information loss,
> complete substitutability), because a registered adapter that seems
> pragmatically useful in one place could mess up unrelated code, since
> registered adapters have global effects.  Perhaps transitivity seems
> dangerous because that has the potential to dramatically increase the
> global effects of those registered adapters.

To put it quite bluntly: many people never bother to implement the
_full_ interface of something if all they need is a half baked
implementation. For example, I may get away with a sequence-like
object in many situations without slice suport in getitem, or a dict
with some of the iteration methods. Call it lazyness, but this is
known to happen quite often, and Python is quite forgiving in this
respect. Add the global scope of the adapter registry & transitivity
to this and things may become much harder to debug...

...but on the other hand, transitivity is a powerful tool in the hands
of an expert programmer, and allows to write much shorter & cleaner
code. Some balance is needed.

-- 
Carlos Ribeiro
Consultoria em Projetos
blog: http://rascunhosrotos.blogspot.com
blog: http://pythonnotes.blogspot.com
mail: carribeiro at gmail.com
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