[Python-Dev] PEP 343 update (with statement context terminology)

[Paul Moore]

On 4/25/06, Nick Coghlan <ncoghlan at gmail.com> wrote:
> PEP 343 made a *deliberate, conscious design decision* to copy the semantics
> of iterators by making the context management protocol a superset of the
> context protocol (or rather, the context specification protocol in alpha 2).

OK. It's possible I'll need to go back to PEP 343 to locate the
justification for this design decision (as I can't find it in the
documentation). I haven't done so thus far, as I am deliberately
trying to retain a position as "newcomer who has only ready the
documentation", because I want to offer that perspective. I've been
drawn so far into design discussions now, that I am probably no longer
of any use in that role.

So now, I'm really just supporting Phillip's side of the discussion.
Which isn't much help, as all we seem to be achieving is a 2 vs 1
impasse, rather than the previous 1 vs 1 :-(

> What I don't understand is why you and Phillip are so keen on breaking this
> deliberate symmetry with an existing part of the language design. Of course it
> isn't necessary, but then neither was it necessary to make the iterator
> protocol a superset of the iterable protocol.

What *I* don't understand, is why the symmetry is so crucial to you.

OK, I'll give in on this one (as Philip has done). I'll accept that
objects providing __enter__ and __exit__ must also provide
__context__. I'll accept your argument above that the parallel with
generators and __iter__ is enough. I'll even accept that the name of
the decorator is the only issue, and it's just a naming and
documentation fix we're after here.

But that leaves one fundamental point (I'm tempted to shout here, but
I won't :-))

I still found the alpha 1 terminology and documentation completely
natural and intuitive. Completely. Not "acceptable", but "completely
natural". From the perspective of someone with limited understanding
of the design, looking to the documentation for enlightenment.

And that's got to be my last word. I can't judge the alpha 2
documentation any more, I'm too close to the problem now. Heck, I no
longer even have usable terms to describe the objects involved,
because every reference has to be qualified with (a1 terminology) or
(a2 terminology).

So I'll bow out at this point. +1 on a1 terminology, can't judge on
anything else. (Oh, and +100000 on just getting the damn thing
resolved once and for all).

I hope my contributions have been useful.

Paul.