Home Original page

[Python-ideas] except expression

Rob Cliffe rob.cliffe at btinternet.com
Wed Feb 19 01:28:30 CET 2014 
On 18/02/2014 22:56, Nick Coghlan wrote:
>
>
> On 19 Feb 2014 06:56, "Chris Angelico" <rosuav at gmail.com 
> <mailto:rosuav at gmail.com>> wrote:
> >
> > My script is currently _very_ simplistic. It looks *only* for
> > assignments, so it won't find something like this:
> >
> > try:
> >     foo.append(args[0])
> > except IndexError:
> >     foo.append('')
> >
> > which is correct, because it's impossible to know whether foo.append()
> > will raise IndexError. (Chances are it won't, especially if we know
> > foo is a list, for instance.) It's not safe to directly translate that
> > sort of thing. It might, however, be something worth improving, as it
> > narrows the scope of the except clause. But if that same code is
> > written thus:
> >
> > try:
> >     tmp = args[0]
> > except IndexError:
> >     tmp = ''
> > foo.append(tmp)
> >
> > then the script _will_ find it, and then it really is a candidate 
> for editing.
>
> This example should go in the PEP - the except clause in the example 
> code is almost certainly too broad, but the fix is rather ugly.
>
> With the PEP, the except clause can easily be moved inside the 
> expression so it doesn't cover the append() call:
>
>     foo.append((args[0] except IndexError: ""))
>
> Cheers,
> Nick.
>
Beautiful catch, Nick!  Shows that this proposal not only gives a neater 
way of writing code without changing the semantics, but may actually 
point the way to _improving_ existing (or new) code.
Rob Cliffe
>
>
>
> _______________________________________________
> Python-ideas mailing list
> Python-ideas at python.org
> https://mail.python.org/mailman/listinfo/python-ideas
> Code of Conduct: http://python.org/psf/codeofconduct/
>
>
> No virus found in this message.
> Checked by AVG - www.avg.com <http://www.avg.com>
> Version: 2012.0.2247 / Virus Database: 3705/6604 - Release Date: 02/18/14
>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/python-ideas/attachments/20140219/666b45b1/attachment-0001.html>
More information about the Python-ideas mailing list