On Tue, May 26, 2020 at 4:12 PM Greg Ewing <greg.ew...@canterbury.ac.nz> wrote:
>
> Wild idea: Instead of sentinels, have a way of declaring optional
> arguments with no default, and a way of conditionally assigning a
> value to them if they are not bound.
>
> E.g.
>
> def order(eggs = 4, spam =):
> spam ?= Spam()
>
> Here the '?=' means "if spam is not bound, then evaluate the
> rhs and assign it, otherwise do nothing."
>
That's interesting. I suppose the semantics would be the same as any
other unbound local, then? That would actually be useful in other
contexts, like where you conditionally assign in a loop, and then
might not have it assigned at the end. I don't know of any current way
to say "if spam is unset".
It definitely needs good syntax though. The loose equals sign would be
too confusing, and there's no good keyword available. It'd be kinda
elegant to surround the name in square brackets:
def order(eggs=4, [spam]):
spam ?= Spam()
but that would be confusing for other reasons.
ChrisA
_______________________________________________
Python-ideas mailing list -- python-ideas@python.org
To unsubscribe send an email to python-ideas-le...@python.org
https://mail.python.org/mailman3/lists/python-ideas.python.org/
Message archived at
https://mail.python.org/archives/list/python-ideas@python.org/message/6ZBEBI6Y7ZFDB7GSJ23V5QNGY7WF2ZT3/
Code of Conduct: http://python.org/psf/codeofconduct/
