The problem with doing that is that it's ambiguous. There's no way of telling which attribute is allowed to coalesce.

I think one of the best arguments for a coalescing operator in Python is that it allows you to be more explicit, without the hassle of nested try: except AttributeError blocks. You lose that with something like attrgetter('b.x.z', coalesce=True) -- it would behave identically, regardless of whether b, x, or z were missing, which is (oftentimes) not what you want.


2016-10-27 15:28 GMT-07:00 Barry Warsaw <barry@python.org>:
On Oct 27, 2016, at 06:27 PM, Joonas Liik wrote:

>perhaps just having a utility function can get us some of the way there..
>
>#may error
>r = a.b.x.z
>
># will default to None
>r = a?.b?.x?.z
>r = get_null_aware(a, "b.x.z") # long but no new syntax, can be
>implemented today.

You could probably do this by extending operator.attrgetter() to take an
optional 'coalesce' keyword.  It wouldn't be super pretty, but it has the
advantage of no magical new syntax.  E.g. your example would be:

from operator import attrgetter
r = attrgetter('b.x.z', coalesce=True)

That might be good enough for honestly how rare I think this use case is.
(Similarly with itemgetter().)

Cheers,
-Barry

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