[Python-Dev] PEP 3102: Keyword-only arguments

[Russell E. Owen]

In article 
<ca471dc20605020744m333c855cqbf9016340ea5d699 at mail.gmail.com>,
 "Guido van Rossum" <guido at python.org> wrote:

> On 5/2/06, Greg Ewing <greg.ewing at canterbury.ac.nz> wrote:
> > Terry Reedy wrote:
> >
> > > my way to call your example (given the data in separate variables):
> > >   make_person(name, age, phone, location)
> > > your way:
> > >   make_person(name=name, age=age, phone=phone, location = location)
> >
> > For situations like that, I've sometimes thought
> > it would be useful to be able to say something like
> >
> >    make_person(=name, =age, =phone, =location)
> 
> And even with Terry's use case quoted I can't make out what you meant
> that to do.

I'm pretty sure he wants it to mean:

make_person(name=name, age=age, phone=phone, location=location).

In other words it's a shortcut to avoid needless repetition.

Personally I'd like some way to do that, but the initial "=" is pretty 
startling at first glance. Not that I have a better suggestion.


As far as the rest of the thread goes (and I may be late to the party on 
this), I personally would *love* to be able to write:
def func(arg0, arg1, *args, key1=def1)
and force key1 to be specified by name. I've coded this before using 
**kargs for the keyword-only args, but I'd much rather be able to list 
them in the def (making it more self-documenting).

But that's as far as I'd take it.

I don't see the point to keyword-only arguments that do not have default 
values. And I don't think it's worth the potential confusion to allow 
keyword-only args after a fixed # of positional args. The proposed 
syntax reads like exactly the wrong thing to me; "|" as a separator 
might do if one is desperate enough for this feature, i.e.:
def foo(arg0, arg1 | karg=None):

-- Russell