Chris Angelico writes:
> ## New "unless" construct for list displays and argument lists ##
>
> Inside a list/dict/set/tuple display, or inside an argument list,
> elements can be conditionally omitted by providing a predicate.
>
> lst = [f1(), f3() unless f2(), f4()]
Not a fan of this in displays, YMMV. IME the cases where I could use
this are generally well-served by comprehensions with if clauses.
(I'm speaking for myself only, I have no idea if others have "more
than once in a blue moon" use cases.)
OTOH
foo(f1(), f3() unless f2(), f4())
looks horrible to me, a definite -1. Yes, I know about varargs
functions, but "positional" means positional to me. Surely this would
almost always be a runtime error in format() if not f2(), for example.
It would have to be used quite frequently for me to get over the
awkwardness, I think.
Granted,
foo(*[f1(), f3() unless f2(), f4()])
is horrid, too (and if you wanted to use a tuple for efficiency it
would be unreadable). But how often would you want to call varargs
with arguments that might not even be there? Would
args = (f1(), f3() unless f2(), f4())
foo(*args)
be so bad for the rare occasion? (Maybe it's not so rare for others,
but I can't recall ever wanting this, while list displays with
variable desired length do come up.)
Steve
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