[Python-Dev] with-statement heads-up

[Guido van Rossum]

On 2/28/06, Nick Coghlan <ncoghlan at gmail.com> wrote:
> Guido van Rossum wrote:
> > I just realized that there's a bug in the with-statement as currently
> > checked in. __exit__ is supposed to re-raise the exception if there
> > was one; if it returns normally, the finally clause is NOT to re-raise
> > it. The fix is relatively simple (I believe) but requires updating
> > lots of unit tests. It'll be a while.
>
> So does that mean with statements *will* be able to suppress exceptions now?
> (If I'm reading the PEP changes right it does, but I haven't finished my
> coffee yet. . .)

Yes. And unless there are peasants at the gate with pitchforks etc. it
will stay that way. :-)

> I'm not complaining if that's so, as I think allowing it makes the operation
> of the statement both more useful and more intuitive, but you were originally
> concerned about the potential for hidden flow control if the context manager
> could suppress exceptions, as well as the need to remember to write "raise" in
> the except clauses of context managers.

Yes, I've changed my mind about that.

> If you changed your mind along the way, that should probably be explained in
> the PEP somewhere :)

I don't know that PEPs benefit from too much "on the one hand, on the
other hand, on the third hand" or "and then I changed my mind, and
then I changed it back, and then I changed it again".

--
--Guido van Rossum (home page: http://www.python.org/~guido/)