Haskell does something similar to this.. ls :: [String] ls = [“hello”, “world”] t :: (String, Int) t = (“hello”, 5) While at it, why don’t we pattern match function parameters like Haskel. Very elegant way for function overload. Something like this … case def func(int(x), [float(y), *_], int(z)) if z != 0 -> int: return int((x + y) / z) case def func(int(x), [float(y), *_], int(z)): -> int: return 0 case def func(_): raise # func(1, [1.2, 3, 5], 3) -> (1 + 1.2) / 3 # func(1, [1.2], 0) -> 0 # func("dummy", [1.2, 3, 5]) -> raise error No need to precede it with the “match” statement because we are pattern matching function parameters here in those cases. Also, annotating the parameters will be redundant. Abdulla
On 28 Jul 2021, at 3:42 AM, Ignacio Pickering <ign.pickering@gmail.com> wrote:
Currently type hints for built-in containers are, in my opinion, less succint than required. I suspect it is probably not very difficult for a type checker to interpret something like this for example:
var1: {str: (int, int)} = {"label": (1, 2)} var2: {str} = {"other_label"}
def function(param1: {int: str} = {1: "foo"}, param2: (int, ...) = (1, 2, 3)) -> (int, (str, ...)): return 3, ("foo", "bar")
as equivalent to:
var1: dict[str, tuple[int, int]] = {"label": (1, 2)} var2: set[str] = {"other_label"}
def function(param1: dict[int, str] = (1, "foo"), param2: tuple[int, ...] = (1, 2, 3)) -> tuple[int, tuple[str, ...]]: return 3, ("foo", "bar")
I thought of posting something like this as a mypy feature suggestion, but I suspect the language would need to modify the way type annotations are interpreted for something like it to work (or maybe not?). Basically, inside a type annotation, the objects created by (a, b), [a], {a: b}, {a} would be reinterpreted as the same thing as constructing tuple[a, b], dict[a, b], list[a], set[a]. I have found myself wanting to write things like this a couple of times, so I think this overloaded usage of builtin containters is natural. I actually feel it is so natural it must either have been proposed before (in which case I would love to give the feature my +1) or there is some more or less obvious flaw. _______________________________________________ Python-ideas mailing list -- python-ideas@python.org To unsubscribe send an email to python-ideas-leave@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/SUYRV7... Code of Conduct: http://python.org/psf/codeofconduct/