On Mar 12, 2014, at 10:40 AM, Ethan Furman wrote: >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
I have to challenge a couple of assertions here. First, that the exception expression is easier to read. I'm not sure it is. I suspect they will tend to be expressed on very long lines, much like ternary expressions are today. PEP 8 then would have you split them across multiple lines, which introduces parentheses or backslashes to accomplish. For ternary expressions, this can get ugly and for me sometimes draws me back to traditional if/else statements. Other times, ternaries can be worth it, but either way, it does (again for me) reduce the readability argument. Interestingly enough, where ternaries are most useful are in the same situations where I think exception expressions would be most useful, in the setting of a variable or attribute to one of two different values. In both branches of the conditional, the left hand side is the same target, and what differs is the value being assigned to the LHS. Looking over exception examples from a large code base, I find it rare (but not nonexistent) that exceptions are used in the same situation. But that could be because I'm so comfortable with .get() and other helpers. Ternary expressions seem more compelling. But there's definitely some overlap, which is perhaps why the colon seems so jarring to me. So the second assertion is that these will be common enough to warrant changing the language. Again, I'm not personally convinced. I echo Guido though: it is a well written PEP, and I commend Chris for navigating the python-dev/python-ideas gauntlet! That's an accomplishment even if the PEP is rejected. Cheers, -Barry _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
