[Python-ideas] Generator syntax hooks?

[Chris Barker]

On Tue, Aug 8, 2017 at 10:06 PM, Nick Coghlan <ncoghlan at gmail.com> wrote:

> On 8 August 2017 at 09:06, Chris Barker <chris.barker at noaa.gov> wrote:
> > It would be nice to have an easier access to an "slice iterator" though
> --
> > one of these days I may write up a proposal for that.
>
> An idea I've occasionally toyed with [1] is some kind of "iterview"
> that wraps around an arbitrary iterable and produces lazy itertools
> based results rather than immediate views or copies.
>
> However, my experience is also that folks are *really* accustomed to
> syntactic operations on containers producing either full live views
> (e.g. memoryview or numpy slices, range as a dynamically computed
> container), or actual copies (builtin container types). Having them
> produce consumable iterators instead then gets confusing due to the
> number of operations that will implicitly consume them (including
> simple "x in y" checks).
>

I agree -- which is why I"m thinking only adding a simple "iterable slice",
rather than changing the overall behavior of the container. It would be
quite clear what you are asking for.

Right now, getting the "terminate when false" behaviour requires the
> use of takewhile:
>

I can't recall the use case(s) at the moment, but I have definitely wanted
a way to break out of a comprehension -- and not always with infinite
iterators.

After all, we have "break" in both for and while loops, so clearly there is
the use case...

If someone comes up with a clean and not confusing (and general purpose)
syntax, I think it would be very useful.

-CHB

-- 

Christopher Barker, Ph.D.
Oceanographer

Emergency Response Division
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Chris.Barker at noaa.gov
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