[Python-Dev] PEP 246, redux

[Alex Martelli]

On 2005 Jan 12, at 18:58, Phillip J. Eby wrote:
    ...
>> I have some data about people coming in from LDAP and the like, which 
>> I want to record in that SQL DB -- the incoming data is held in types 
>> that implement IPerson, so I write an adapter IPerson -> IFullname 
>> for the purpose.
>
> This doesn't answer my question.  Obviously it makes sense to adapt in 
> this fashion, but not IMPLICITLY and AUTOMATICALLY.  That's the 
> distinction I'm trying to make.  I have no issue with writing an 
> adapter like 'PersonAsFullName' for this use case; I just don't think 
> you should *register* it for automatic use any time you pass a Person 
> to something that takes a FullName.

I'm adapting incoming data that can be of any of a huge variety of 
concrete types with different interfaces.  *** I DO NOT WANT TO 
TYPECHECK THE INCOMING DATA *** to know what adapter or converter to 
apply -- *** THAT'S THE WHOLE POINT *** of PEP 246.  I can't believe 
we're misunderstanding each other about this -- there MUST be 
miscommunication going on!


>>   So, I'm not sure why you appear to argue for conversion against 
>> adaptation, or explicit typechecking against the avoidance thereof 
>> which is such a big part of adapt's role in life.
>
> Okay, I see where we are not communicating; where I've been saying 
> "conversion", you are taking this to mean, "don't write an adapter", 
> but what I mean is "don't *register* the adapter for implicit 
> adaptation; explicitly use it in the place where you need it.

"Adaptation is not conversion" is how I THOUGHT we had agreed to 
rephrase my unfortunate "adaptation is not casting" -- so if you're 
using conversion to mean adaptation, I'm nonplussed.

Needing to be explicit and therefore to typechecking/typeswitching to 
pick which adapter to apply is just what I don't *WANT* to do, what I 
don't want *ANYBODY* to have to do EVER, and the very reason I'm 
spending time and energy on PEP 246.  So, how would you propose I know 
which adapter I need, without spreading typechecks all over my 
bedraggled *CODE*?!?!


Alex