[Python-ideas] A better (simpler) approach to PEP 505

[David Mertz]

On Mon, Jul 23, 2018 at 12:47 PM Antoine Pitrou <solipsis at pitrou.net> wrote:

> > favorite = cfg?.user?.profile?.food ?? "Spam"
> > favorite = NoneAware(cfg, "Spam").user.profile.food.unbox()
>


> You could use .__call__() instead of .unbox().  Also you can make
> unboxing unnecessary in most cases by having your class proxy most
> operations, like weakref.proxy does.  The "wrapt" library may help with
> that: http://wrapt.readthedocs.io/en/latest/wrappers.html


I'm not sure I entirely understand how that class proxy could be made
transparent.  Maybe you can make a toy implementation to show me?  How can
we make this work?

    favorite = NoneAware(cfg, "Spam").user.profile.food + "and more spam"

I just noticed in my scratch directory that I had implemented almost the
same thing a year ago when this discussion last came up.  It's simple
enough that the code was almost the same back then.  I had included
`.__getitem__()` in that version, but had not considered sentinels.

However, one thing I *did* implement was `.__call__()`, but that reminds me
of why your idea cannot work.  I had it either call or fall back to more
boxing.  The end point of the chained attributes (or dict lookups) can
perfectly well be a callable.  E.g.

    favorite = NoneAware(cfg, "Spam").user.profile.get_food()

Well, that's not going to work in my current toy code either since it would
need to be:

    favorite = NoneAware(cfg, "Spam").user.profile.get_food.unbox()()

But I could implement special stuff for "if the tail is a callable, unbox
it automatically", I suppose.

However, it would be fundamentally ambiguous, I think, whether those final
parens should mean "unbox" or "call".  Or I guess if calling *always* meant
"unbox" we could have:

    favorite = NoneAware(cfg, "Spam").user.profile.get_food()()

That feels weird to me though.

-- 
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advocates of freedom in prisons.  Intellectual property is
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