> > Efforts to improve Py3.0 have spilled > > over into breaking Py2.x code with no compensating benefits. [...] > > We don't have to wreck 2.x in order to make 3.0 better. > > I think you're overstating things a bit here.
It's only an overstatement if Guido didn't mean what he said. If bare except clauses are deprecated in 2.x, it WILL affect tons of existing code and invalidate a portion of almost all Python books. > > Remember, the ONLY benefit from the whole PEP is that in 3.0, it will no > > longer be necessary to write "except (KeyError, SystemExit): raise". > > [...] IOW, there's nothing worth inflicting destruction on tons of > > 2.x code. > > And now I *KNOW* you're overstating things. There are LOTS of benefits > to the PEP in 3.0. My own personal favorite is that users can be > guaranteed that all exceptions thrown will share a particular common > ancestor and type. Right, there are a couple of parts of the PEP that were non-controversial from the start and would likely have happened even in the absence of the PEP. My point was that a lot of machinery is being thrown at a tiny problem. To eliminate the need for "except (KeyError, SystemExit): raise", we're rearranging the tree, introducing a new builtin, banning an existing and popular form of an except clause, and introducing a non-trivial deprecation that will affect most users. This is a lot of firepower directed at a somewhat small problem. > But no syntax will work in BOTH 2.5 and 3.0. There's the rub. If you can't write code that will work for both, then there is no reason to force 2.x users to make any changes to their existing code, especially given that they won't see any benefit from the mass edits. > If we cannot produce a warning for these, then I'd > rather not produce the warning for the use of bare "except:". > After all, as it's been pointed out, if the use of bare "except:" > is all you are interested in it is quite easy to grep the code to > find all uses. Bingo. A bare except clause is well known as a consenting adults construct. If Guido feels driven to eliminate it from Py3.0, then that is the way it is. But for 2.x, why introduce unnecessary pain. Of course, if bare except clauses weren't banned for 3.0, then we would have no problem writing code that works on all versions on Python from 2.0 to 3.0, that doen't break existing code, and that doesn't invalidate the text in Python books. IMO, that is a nice situation. Just how badly do you want to kill bare except clauses. I propose that leave them alone, and be happy that in 3.0 we can write "except Exception" and get what we want without any fuss. Raymond _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
