[Python-ideas] Null coalescing operators

[Oleg Broytman]

On Sun, Sep 20, 2015 at 12:05:52PM +0100, Paul Moore <p.f.moore at gmail.com> wrote:
> On 20 September 2015 at 08:31, Steven D'Aprano <steve at pearwood.info> wrote:
> > I'm not convinced that we should generalise this beyond the three
> > original examples of attribute access, item lookup and function call. I
> > think that applying ? to arbitrary operators is a case of "YAGNI". Or
> > perhaps, "You Shouldn't Need It".
> 
> Agreed.
> 
> Does this need to be an operator? How about the following:
> 
>     class Maybe:
>         def __getattr__(self, attr): return None
>         def __getitem__(self, idx): return None
>         def __call__(self, *args, **kw): return None
> 
>     def maybe(obj):
>         return Maybe() if obj is None else obj
> 
>     attr = maybe(obj).spam
>     elt = maybe(obj)[n]
>     result = maybe(callback)(args)
> 
> The Maybe class could be hidden, and the Maybe() object a singleton
> (making my poor naming a non-issue :-)) and if it's felt sufficiently
> useful, the maybe() function could be a builtin.
> 
> Usage of the result of maybe() outside of the above 3 contexts should
> simply be "not supported" - don't worry about trying to stop people
> doing weird things, just make it clear that the intent is only to
> support the 3 given idiomatic usages.

   PyMaybe - a Python implementation of the Maybe pattern. Seems to be
quite elaborated.

https://github.com/ekampf/pymaybe

> Paul.

Oleg.
-- 
     Oleg Broytman            http://phdru.name/            phd at phdru.name
           Programmers don't die, they just GOSUB without RETURN.