[Python-Dev] pep 310 (reliable acquisition/release pairs)

[Holger Krekel]

Michael Hudson wrote:
> Holger Krekel <hpk at trillke.net> writes:
> > The PEP actually is about interacting with the execution 
> > of a code block.  It allows to define (one-shot) interception points 
> > for entering and leaving a code block.  Now there are at least 
> > two interesting cases which the PEP does (quite explicitely) not cover:
> >
> > - what to do with exceptions 
> >
> > - what to do with yield 
> >
> > IMHO introducing a new block statement at this stage in language 
> > development warrants an effort to tackle these cases (and maybe more
> > like e.g. allowing the handler to trigger looping). 
> >
> > This is probably best done with trying to directly design a protocol between
> > the "interpreter-loop" and the - what i'd call - the "execution handler". 
> 
> Well, in writing PEP 310 (as I suspect you know) I was aiming for a
> simple, almost entirely syntactic way of shortening a common pattern.
> You seem to be gunning for something far deeper here.

Hmmm, introducing a new block statement just for "shortening a common
pattern" doesn't sound like a sufficient reason to me.  OTOH i'd try to argue
that in order to add reliable resource synchronization an effort to get 
it working in the context of exceptions and generators would add more 
than just a macro :-) 

Also thinking more along the lines of Armin's alternative idea
(incorporate it in into the for-loop protocol) is interesting as
it avoids adding a new keyword which seems of great value to me. 

on a side note, it would be great if we could soon (after integration of the 
parser/compiler) branch off PyPy to do quick experiments with different
approaches.  IIRC Guido mentioned at EuroPython that this might
be an interesting use of PyPy (to easily test new language features). 
This way it's also easier for PyPy to keep up to date :-)

cheers,

    holger