Aaron Brady wrote:

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-----Original Message----- From: python-ideas-bounces@python.org [mailto:python-ideas- bounces@python.org] On Behalf Of Ron Adam

def f(; a, b=2, c=3;): No positional only, no keyword only

Do you prohibit defaults in type 1, the pos-only?

No

Not necc. Does this look right?

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def f( a=0; b=1 ): ... print a, b f() 0, 1

That's fine. 'a' is positional only and 'b' is either. Having defaults and being positional only are two different things. With the above function the following would be allowed. f() f(1) f(1, 2) f(1, b=2) f(b=2) But not: (If positional only also means no assignment with keywords at call time.) f(a=1) # Keyword not allowed for 'a' at call time. f(b=2, a=1) # 'a' is positional only

Also, does this look right?

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def f( a=0; b ): ... print a, b File "<stdin>", line 1 SyntaxError: non-default argument follows default argument

Looks ok to me. Even the error is correct.

Any more groups? So far I have pos-only, pos-or-kw, and kw-only.

If not, a ascii character works fine to delimit, like * and **.

Any character can possibly do it, but does it make sense given that they already have a meaning? I have a feeling we are trying to do too much at once. required optional with default with out default in order in order only with keyword with keyword only Can these be ordered into *any* decision tree that makes sense?

Do we want to annotate each parameter individually? This could get out of hand. But decorators won't let you do

@f( k ) def j( k ): ...

where

@f( 'k' ) def j( k ): ...

gets unwieldy and could show promise. Cf. Steven's positional only arguments decorator.

I think we should let Steven's decorator be developed further. It will at least give a way to test ideas and find more use cases. Then if there are some frequent and common use cases. Then look at what is actually needed. Cheers, Ron