[Python-ideas] Fwd: Null coalescing operator

[David Mertz]

On Sat, Sep 10, 2016 at 5:23 PM, Guido van Rossum <guido at python.org> wrote:

> No. PEP 505 actually solves the problem without ever catching
> AttributeError. Please read it.
>

I read it again (I did a year ago, but reviewed it now).  I hadn't been
thinking that the *mechanism* of a new None-coalescing operator would
actually be catching an exception.  It could (and should) work differently
if it becomes syntax.

What I was getting at with "essentially" was that it would *do the same
thing* that an AttributeError does.  That is, if `x.foo` can't be evaluated
(i.e. x doesn't have an attribute 'foo'), then access is informally "an
error."  The hypothetical "x?.foo" catches that "error" and substitutes a
different value.  The particular implementation under-the-hood is less
important for most programmers who might use the construct (and I think
documentation would actually give an informal equivalent as something
similar to what I put in the NoneCoalesce class).


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