Aahz wrote:
> [holger krekel]
> >
> > def __enter__(self):
> > "before suite start"
> >
> > def __except__(self, type, value, tb):
> > "swallow given exception, reraise if neccessary"
> >
> > def __leave__(self):
> > """upon suite finish (not called if __except__
> > exists and an exception happened)
> > """
>
> No, __leave__/__exit__ should always be called regardless of whether an
> exception hits. That's the whole point of this proposal, IMO.
The __except__ hook (like all others) is optional. Always invoking
__except__ and __leave__ would amount to a try-except-finally clause
which is seldomly needed and not existing today.
Most often you either have exception handling or finally-handling.
Anyway, it is no problem to invoke __leave__ from within __except__ if
this is really neccessary (it hasn't been with my use cases).
And __leave__ does get invoked if there is no __except__.
> > One remark (mainly to Michael as he does that other
> > patch) about the hook-name __leave__ versus __exit__.
> > we may want to eventually allow 'yield' within the
> > thunk and then '__exit__' would be misleading. Here is
> > the use case:
> >
> > exec self.mylock: # would lock/unlock on entering/leaving
> > # the generator
> > ...
> > for whatever in something:
> > yield whatever
> > ...
>
> I'm thinking that this is *way* too complex.
If yield would be allowed inside try-finally then this
would be straight forward IMO. Obviously, today there is
a semantic problem because it is unclear if the finally-code
should be executed multiple times.
But with the exec/with proposal this can be cleanly
defined from the start (enter/leave) *just in case*
that we ever want to allow yield within the new
thunk-construct.
Actually, I am just arguing that the "finish" hook should be
named '__leave__' rather than '__exit__' because the latter
sounds like "completly finished". I don't think it hurts even
if we never allow yield within try-finally.
regards,
holger
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