[Python-Dev] Requesting pronouncement on PEP 463: Exception-catching expressions (original) (raw)

Ethan Furman ethan at stoneleaf.us
Wed Mar 12 18:40:59 CET 2014

On 03/12/2014 10:09 AM, Guido van Rossum wrote:

I want to reject this PEP. [...] But the thing I can't get behind are the motivation and rationale. I don't think that e.g. dict.get() would be unnecessary once we have except expressions, and I disagree with the position that EAFP is better than LBYL [...]

Does this mean a better motivation and rationale may cause you to change your mind?

My motivation is for simpler, easier to read code: instead of a full-blown try/except block or a double-lookup into an indexable object I would much rather do:

 self.date = text_to_date(date, 'mdy') except ValueError: batch_date

instead of:

 try:
     self.date = text_to_date(date, 'mdy')
 except ValueError:
     self.date = batch_date

This is probably the most you can get out of me as far as a pronouncement. Given that the language summit is coming up I'd be happy to dive deeper in my reasons for rejecting it there (if there's demand).

I would like to know, but I won't be at the language summit. I can wait until after, though -- I know time is in especially short supply until then.

-- Ethan

More information about the Python-Dev mailing list