[Python-Dev] Merging PEP 310 and PEP 340-redux?

[Phillip J. Eby]

At 10:42 AM 5/11/2005 -0700, Guido van Rossum wrote:
>[Phillip J. Eby]
> > FYI, there are still use cases for clearing the exception state in an
> > __exit__ method, that might justify allowing a true return from __exit__ to
> > suppress the error.  e.g.:
>[...]
>
>Yes, but aren't those written clearer using an explicit try/except?
>IMO anything that actually stops an exception from propagating outward
>is worth an explicit try/except clause, so the reader knows what is
>happening.

I thought the whole point of PEP 340 was to allow abstraction and reuse of 
patterns that currently use "try" blocks, including "except" as well as 
"finally".  So, if you're only going to allow try/finally abstraction, 
wouldn't it make more sense to call it __finally__ instead of 
__exit__?  That would make it clearer that this is purely for try/finally 
patterns, and not error handling patterns.

As for whether they're written more clearly using an explicit try/except, I 
don't know.  Couldn't you say exactly the same thing about explicit 
try/finally?  For that matter, if you used function calls, doesn't it 
produce the same issue, e.g.:

     def retry(count,exc_type=Exception):
         def attempt(func):
             try: func()
             except exc_type: pass
         for i in range(count-1):
             yield attempt
         yield lambda f: f()

     for attempt in retry(3):
         attempt(somethingThatMightFail)

Is this bad style too?