Ok, maybe: def foo(x=:[], y=:len(x)):
As a shorthand for: @default(x=lambda: [], y=lambda x: len(x)) def foo(x=None, y=None): =: Is the contraction for =lambda: At the same time, this new syntax avoid breaking def foo(x=lamba: []) which is completely different as we know. Le jeu. 11 févr. 2021 à 04:03, Chris Angelico <ros...@gmail.com> a écrit : > On Thu, Feb 11, 2021 at 1:55 PM J. Pic <j...@yourlabs.org> wrote: > > > > Adding decorators with some inspect sauce could certainly work with the > syntax we already have: > > > > @default(x=lambda: copy([]), y=lambda x: len(x)) > > def foo(x=None, y=None): > > This would work, although the copy is unnecessary here. But you're > assuming that it magically figures out whether to pass 'x' or not. > Seems awkward. Also, it doesn't solve the problems of signature > display, so you're not really much better than: > > def foo(x=None, y=None): > if x is None: x = [] > if y is None: y = len(x) > > > I think this PoC is doable. But the lambda copy is a boring so, two > decorators: > > > > @default.copy(x=[]) > > @default.call(y=lamba x: len(x)) > > def foo(x=None, y=None): > > > > Or with a new syntax: > > > > def foo(x:=[], y`=len(x)) > > Now this is the sort of thing I was talking about: actual syntactic > support. But this syntax looks pretty terrible, and if you propose it > like this, I doubt it'll be accepted. Backtick had a very very > different meaning in Py2, and := is going to be extremely confusing. > > This proposal will stand or fall on the syntax. Don't just give > placeholder syntax. Put some thought into figuring out what would > actually be good, and propose *that*. The semantics aren't really even > that hard - it'd be equivalent to an if statement just inside the > function. > > ChrisA > -- > https://mail.python.org/mailman/listinfo/python-list > -- https://mail.python.org/mailman/listinfo/python-list
