On Sat, Oct 23, 2021 at 6:20 AM Marc Mueller <cdce8p@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