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

[Phillip J. Eby]

At 12:49 PM 4/24/2006 -0700, Aahz wrote:
>On Mon, Apr 24, 2006, Phillip J. Eby wrote:
> > At 12:24 PM 4/24/2006 -0700, Aahz wrote:
> >>On Mon, Apr 24, 2006, Phillip J. Eby wrote:
> >>> At 04:48 AM 4/25/2006 +1000, Nick Coghlan wrote:
> >>>>
> >>>>Using two names to describe three different things isn't intuitive for
> >>>>anybody.
> >>>
> >>> Um, what three things?  I only count two:
> >>>
> >>> 1. Objects with __context__
> >>> 2. Objects with __enter__ and __exit__
> >>>
> >>> What's the third thing?
> >>
> >>The actual context that's used during the execution of BLOCK.  It does
> >>not exist as a concrete object,
> >
> > Um, huh?  It's a thing but it's not an object?  I'm lost now.  I don't see
> > why we should introduce a concept that has no concrete existence into
> > something that's hard enough to explain when you stick to the objects that
> > actually exist.  :)
>
>Let's go back to a pseudo-coded with statement:
>
>     with EXPRESSION [as NAME]:
>         BLOCK
>
>What happens while BLOCK is being executed?  Again, here's what I said
>originally:
>
>     EXPRESSION returns a value that the with statement uses to create a
>     context (a special kind of namespace).  The context is used to
>     execute the BLOCK.  The block might end normally, get terminated by
>     a break or return, or raise an exception. No matter which of those
>     things happens, the context contains code to clean up after the
>     block.
>
>Do you have an alternate proposal for describing this that works well for
>newbies?

No, I like your phrasing -- but it's quite concrete.  EXPRESSION returns a 
value (object w/__context__) used to create a context (object w/__enter__ 
and __exit__).

That's only two things.  There is no *third* thing here.