On Apr 22, 2005, at 16:51, holger krekel wrote:
Moreover, i think that there are more than the "transactional" use cases mentioned in the PEP. For example, a handler may want to log exceptions to some tracing utility or it may want to swallow certain exceptions when its block does IO operations that are ok to fail.
I entirely agree! In fact, I was discussing this very issue recently with colleagues at Google, most of them well acquainted with Python but not all of them Python enthusiasts, and I was surprised to see unanimity on how PEP 310 *with* __except__ would be a huge step up in usefulness wrt the simple __enter__/__exit__ model, which is roughly equivalent in power to the C++ approach (destructors of auto variables) whose absence from Python and Java some people were bemoaning (which is how the whole discussion got started...).
The use cases appear to be aleph-0 or more...;-). Essentially, think of it of encapsulating into reusable forms many common patterns of try/except use, much like iterators/generators can encapsulate looping and recursive constructs, and a new vista of uses open up...
Imagine that in two or three places in your code you see something like...
try:
...different blocks here...
except FooError, foo:
# some FooError cases need whizbang resetting before they propagate
if foo.wobble > FOOBAR_RESET_THRESHOLD:
whizbang.reset_all()
raiseWith PEP 310 and __except__, this would become:
with foohandler: ...whatever block..
in each and every otherwise-duplicated-logic case... now THAT is progress!!!
IOW, +1 ... !
Alex
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