[Python-Dev] Son of PEP 246, redux

[Alex Martelli]

On 2005 Jan 13, at 03:57, Phillip J. Eby wrote:

> Okay, I'm really out of time now.  Hate to dump this in as a possible 
> spoiler on PEP 246, because I was just as excited as Alex about the 
> possibility of it going in.  But this whole debate has made me even 
> less enamored of adaptation, and more interested in finding a cleaner, 
> more intuitive way to do it.

Perfectly reasonable, of course.  Doubts about the class / inheritance 
/ interface / instance / method / ... "canon" as the OTW to do OOP are 
almost as old as that canon itself, and have evolved along the years, 
producing many interesting counterexamples and variations, and I fully 
share your interest in them.  Adaptation is rather ``ensconced'' in 
that canon, and the conceptual and practical issues of IS-A which 
pervade the canon are all reflected in the new ``(can be automatically 
adapted to be used) AS-A'' which adaptation introduces.  If adaptation 
cannot survive some vigorous critical appraisal, it's much better to 
air the issues now than later.

Your proposals are novel and interesting.  They also go WAY deeper into 
a critical reappraisal of the whole object model of Python, which has 
always been quite reasonably close to the above-mentioned "canon" and 
indeed has been getting _more_ so, rather than less, since 2.2 (albeit 
in a uniquely Pythonical way, as is Python's wont -- but not 
conceptually, nor, mostly, practically, all that VERY far from canonic 
OOP).  Moreover, your proposals are at a very early stage and no doubt 
need a lot more experience, discussion, maturation, and give-and-take.

Further, you have indicated that, far from _conflicting_ with PEP 246, 
your new ideas can grow alongside and on top of it -- if I read you 
correctly, you have prototyped some variations of them using PEP 246 
for implementation, you have some ideas of how 'adapt' could in turn be 
recast by using your new ideas as conceptual and practical foundations, 
etc, etc.

So, I think the best course of action at this time might be for me to 
edit PEP 246 to reflect some of this enormously voluminous discussion, 
including points of contention (it's part of a PEP's job to also 
indicate points of dissent, after all); and I think you should get a 
new PEP number to use for your new ideas, and develop them on that 
separate PEP, say PEP XYZ.  Knowing that a rethink of the whole 
object-model and related canon is going on at the same time should help 
me keep PEP 246 reasonably minimal and spare, very much in the spirit 
of YAGNI -- as few features as possible, for now.

If Guido, in consequence, decides to completely block 246's progress 
while waiting for the Copernican Revolution of your new PEP XYZ to 
mature, so be it -- his ``nose'' will no doubt be the best guide to him 
on the matter.  But I hope that, in the same pragmatic and minimalist 
spirit as his "stop the flames" Artima post -- proposing minimalistic 
interfaces and adaptation syntax as a starting point, while yet keeping 
as a background reflection the rich and complicated possibilities of 
parameterized types &c as discussed in his previous Artima entries -- 
he'll still give a minimalistic PEP 246 the go-ahead so that 
widespread, real-world experimentation with adaptation and his other 
proposals can proceed, and give many Pythonistas some practical 
experience which will make future discussions and developments much 
sounder-based and productive.


So, what do you think -- does this new plan of action sound reasonable 
to you?


Alex