On 2019-04-24 22:42, Guido van Rossum wrote:
Thanks for posting. I agree that Callable is ugly (even hideous :-), but
when we introduced type annotations in PEP 484, we didn't want to
introduce new syntax. The existing syntax (using -> in function
headings) was supported since Python 3.0.
Since then we've introduced other new syntax (in particular PEP 526) so
we could indeed try adding something better for Callable.
I think we should probably at least have parentheses around the
arguments, so you'd write
f: (int) -> str
g: (int, str) -> float
That looks elegant.
But we should also try to support optional arguments and keyword arguments.
Also, some groups of people would like to see a more concise notation
for lambdas, and maybe they'd want to write
x = (a, b) -> a + b
as sugar for
x = lambda a, b: a + b
We probably can't have both, so we should at least decide which is more
important.
Too bad we can't use Unicode arrows. :-)
Some languages use ->; some others use =>.
As Python already uses -> for the return type, it could use => for lambdas.
On Wed, Apr 24, 2019 at 2:30 PM Vaibhav Karve <vaibhavska...@gmail.com
<mailto:vaibhavska...@gmail.com>> wrote:
(Note: This idea is about a particular static typecheking (typing?)
annotation syntax).
The idea is that currently the use of the "->" (right arrow) is
restricted to only function definition annotation. Can we extent it
to declaration of type for functions even outside their definitions?
Example:
Currently we write:
f: Callable[[int, Dict[str, int]], str] # declaring the type
of some fake function
This would be much cleaner if we could write:
f: int -> Dict[str, int] -> str # One of the possibilities
or even:
f: int, Dict[str, int] -> str # Another possibility
I have no idea how this will affect the existing syntax (and if this
will have any bad repercussions/notational misuse). I just thought
it would be nicer to:
a) Not have to spell out Callable
b) Not have to use all those square brackets
c) Have the same notation work for both the function annotation as
well as for declaring the type.
This is my first time posting an idea to python-ideas. So apologies
if i am not following some conventions that i might not be aware of.
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