On Fri, Aug 7, 2020 at 6:01 PM Paul Moore <p.f.mo...@gmail.com> wrote:
> On Fri, 7 Aug 2020 at 22:46, Ricky Teachey <ri...@teachey.org> wrote:
> >
> > This was inspired by a tweet today from Brandon Rhodes. I looked for
> something like it on the mypy issues page and didn't find anything.
> >
> > Would it make good semantic sense- and be useful- to specify valid
> numerical ranges using slices and type-hint syntax? My suggestion would be
> to, at minimum, provide this functionality for int and float.
> >
> > Consider that currently we have:
> >
> > x: int # this means "all ints", today
> > x: float # this means "all floating point numbers", today
> >
> > Idea in a nutshell would be for the following type declarations to mean:
> >
> > x: int[0:] # any ints greater than or equal to zero would match, others
> would fail
> > x: int[:101] # any ints less than 101 match
> > x: int[0:101:2] # even less than 101
>
> I suspect the biggest issue with this is that it's likely to be
> extremely hard (given the dynamic nature of Python) to check such type
> assertions statically. Even in statically typed languages, you don't
> often see range-based types like this. And type assertions don't do
> runtime checks, so if they can't be usefully checked statically, they
> probably aren't going to be of much benefit (documentation is
> basically all).
>
> Paul
You could be right and I don't know much about this subject.
However the question that comes up for me, though, is: how does TypedDict
perform its static checks? It seems like this:
class D(typing.TypedDict):
a: int
d: D = dict(b=2) # error
Shouldn't be any harder to type check than this:
x: int[0:] = -1 # error
No?
---
Ricky.
"I've never met a Kentucky man who wasn't either thinking about going home
or actually going home." - Happy Chandler
>
_______________________________________________
Python-ideas mailing list -- python-ideas@python.org
To unsubscribe send an email to python-ideas-le...@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/JRAGJ5RUJI2IWKKKT6HQHDDLKOPGGPP5/
Code of Conduct: http://python.org/psf/codeofconduct/
