[Python-ideas] Re: PEP 671: Syntax for late-bound function argument defaults

On 10/24/21 11:22 PM, Steven D'Aprano wrote:

On Sun, Oct 24, 2021 at 05:40:55PM +0100, Jonathan Fine wrote:

...

def puzzle(*, a=>b+1, b=>a+1): return a, b

We can consider that to be syntactic sugar for:

def puzzle(*, a=None, b=None): if a is None: a = b+1 if b is None: b = a+1

So that has a perfectly sensible interpretation:

- a is optional - b is optional - but you must supply at least one.

and should be perfectly legal. I see no reason to prohibit it.

(It would be nice if we could give a better exception, rather than just UnboundLocalError, but that's not essential.)

+1