[Python-ideas] PEP 505: None-aware operators

[Stephan Houben]

FWIW, I like ??

It is short and distinctive.
There is prior art in this spelling in c#.
It requires no new keyword, nor does it give new meaning to an existing one.

I understand why  ?[ needs to be spelled using only a single ?, but I am
afraid it will be used infrequently, and people will accidentally write
 a??[x]
which is legal but different.

I found the example code in the PEP using ?. and ?[ hard to read.
?? and ??= are compelling, though.

One more question: what does this do?

del x
x ??= 42

Stephan


Op do 19 jul. 2018 15:00 schreef Judah Levy <judah.j.levy at gmail.com>:

> On Thu, Jul 19, 2018 at 8:47 AM Rhodri James <rhodri at kynesim.co.uk> wrote:
>
>> On 19/07/18 09:33, Antoine Pitrou wrote:
>> > There is a use case I sympathize with: the argument-is-None case.  For
>> > that I would suggest a simpler form:  "A else B" which would evaluate
>> > to A if A is not None, otherwise to B (parentheses may be mandatory).
>> >
>> > So e.g. one of the examples would read:
>> >
>> >       def insort_right(a, x, lo=0, hi=None):
>> >           # ...
>> >           hi = hi else len(a)
>> >           # ...
>>
>> Much as I would like a keyword, "else" is the wrong one.  It implies we
>> are dealing with truthiness, which we aren't, and lays a subtle semantic
>> trap as a consequence.
>>
>> If anyone can think of a good word for "if it isn't None, otherwise",
>> I'd be all for it :-)
>>
>> --
>> Rhodri James *-* Kynesim Ltd
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>
> I think that it may look better with the order switched and the word
> unless, as in
>
>     def insort_right(a, x, lo=0 hi=None):
>         # ...
>         hi = len(a) unless hi
>         # ...
>
> Unfortunately, this does maybe feel more like checking for truthiness than
> non-Null value
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