On Sat, Oct 23, 2021 at 6:20 AM Marc Mueller <cdc...@gmail.com> wrote: > > Most of the discussion so far has been focused on (?.). Tbh though, I'm more > interested in (??) and (??=). Just reading through code, I constantly notice > boilerplate like this which could easily be substituted. > > variable = some_function(...) > if variable is None: > variable = [] # some default value > > # a bit better with an assignment expression > if (variable := some_function(...)) is None: > variable = [] > > # or worse with an if expression > variable = some_function(...) if some_function(...) else [] > # also possible with :=, but not much better > variable = x if (x := some_function(...)) else []
Bear in mind that these last ones are exactly equivalent to the "or" operator, as they'll use the default if you have any falsy value. variable = some_function(...) or [] > # using the coalesce operator would be much more readable IMO > variable = some_function(...) ?? [] > > If (?.) and (?[) are rejected / deferred, maybe there is interest in seeing > at least (??) and (??=) through? I'm actually more interested in a better idiom for non-constant function default arguments, since that's the place where this kind of thing often comes up. A nice ??= operator might help if your default is None, but if you then change the default to be object(), you can't use ??= any more. As a bonus, the docs for such an argument could actually say what the default really is: def bisect_right(a, x, lo=0, hi=len(a), *, key=None): ... except that it'd need some adornment to say that it's late-bound. ChrisA _______________________________________________ Python-Dev mailing list -- python-dev@python.org To unsubscribe send an email to python-dev-le...@python.org https://mail.python.org/mailman3/lists/python-dev.python.org/ Message archived at https://mail.python.org/archives/list/python-dev@python.org/message/DAD32U6CKSWB3HI322WRKRYYKFNWFPEP/ Code of Conduct: http://python.org/psf/codeofconduct/
