On Thu, Jul 26, 2018 at 11:45 AM, Nicholas Chammas <nicholas.cham...@gmail.com> wrote: > On Wed, Jul 25, 2018 at 9:20 PM Chris Angelico <ros...@gmail.com> wrote: >> >> On Thu, Jul 26, 2018 at 11:02 AM, David Mertz <me...@gnosis.cx> wrote: >> > That is disingenuous, I think. Can this raise an AttributeError? >> > >> > spam?.eggs?.bacon >> > >> > Of course it can! And this is exactly the pattern used in many examples >> > in >> > the PEP and the discussion. So the PEP would create a situation where >> > code >> > will raise AttributeError in a slightly—and subtly—different set of >> > circumstances than plain attribute access will. >> >> I don't understand. If it were to raise AttributeError, it would be >> because spam (or spam.eggs) isn't None, but doesn't have an attribute >> eggs (or bacon). Exactly the same as regular attribute access. How is >> it slightly different? Have I missed something? > > > That was my reaction, too. > > food = spam?.eggs?.bacon > > Can be rewritten as: > > food = spam > if spam is not None and spam.eggs is not None: > food = spam.eggs.bacon > > They both behave identically, no? Maybe I missed the point David was trying > to make.
Aside from questions of repeated evaluation/assignment, yes. The broad semantics should be the same. (If you want to get technical, "spam" gets evaluated exactly once, "spam.eggs" a maximum of once, and "food" gets assigned exactly once. Your equivalent may evaluate and assign multiple times.) ChrisA _______________________________________________ Python-ideas mailing list Python-ideas@python.org https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct: http://python.org/psf/codeofconduct/
