[Python-ideas] Null coalescing operator

[Pavol Lisy]

On 10/31/16, Guido van Rossum <guido at python.org> wrote:

> For "everything to the right" it would seem we have some freedom: e.g. if
> we have "foo.bar?.baz(bletch)" is the call included? The answer is yes --
> the concept we're after here is named "trailer" in the Grammar file in the
> source code (
> https://github.com/python/cpython/blob/master/Grammar/Grammar#L119), and
> "primary" in the reference manual (
> https://docs.python.org/3/reference/expressions.html#primaries). This means
> all attribute references ("x.y"), index/slice operations ("x[...]"), and
> calls ("x(...)").
>
> Note that in almost all cases the "?." operator will be used in an context
> where there is no other operator of lower precedence before or after it --
> given the above meaning, it doesn't make a lot of sense to write "1 + x?.a"
> because "1 + None" is always an error (and ditto for "x?.a + 1"). However
> it still makes sense to assign such an expression to a variable or pass it
> as an argument to a function.
>
> So you can ignore the preceding four paragraphs: just remember the
> simplified rule (indented and in bold, depending on your email client) and
> let your intuition do the rest. Maybe it can even be simplified more:
>
>
> *The "?." operator splits the expression in two parts; the second part is
> skipped if the first part is None.*
>
> Eventually this *will* become intuitive. The various constraints are all
> naturally imposed by the grammar so you won't have to think about them
> consciously.
>
> --Guido

If we skip function call then we also skip argument evaluation?

def fnc():
    print('I am here')

None(fnc())  # behavior similar to this?
None()[fnc()]  # or to this?

PL