The very common use case for creating slice objects is in Pandas and similar libraries. Xarray certainly, or Blaze, to a lesser extent NumPy.
That said, it's very easy to define a suitable __getitem__, as Guido shows. It's really a question simply of whether that object should be named 'slice' or something else. On Nov 12, 2016 5:08 PM, "Guido van Rossum" <gu...@python.org> wrote: > On Sat, Nov 12, 2016 at 11:41 AM, Ivan Levkivskyi <levkivs...@gmail.com> > wrote: > >> On 12 November 2016 at 20:27, David Mertz <me...@gnosis.cx> wrote: >> >>> I thought of the use of `.__getitem__()` in metaclasses in the typing >>> module. I feel like this use is more natural and more useful than that. >>> Should we someday need a slice generic type for PEP 484, the spelling would >>> naturally be `Slice[T]` instead, in my mind. But `slice[1:10,2]` should be >>> a constructor for a concrete slice object. >>> >> >> Slice[T] vs slice[::-1] is coherent with what we have now for List[T] vs >> list, etc. >> > > Not really. We have List[T] but list[x] is invalid -- it doesn't have a > different meaning (it's list instances that support indexing). And in fact > the distinction between List and list is intentionally minimal -- List is > simply what list wants to become when it grows up. :-) > > Honestly I think the use case of wanting to create a slice object is rare > enough that we can continue to write slice(x, y, z). If you really find > yourself wanting something shorter, I believe in the past it's been pointed > out that you could create a helper, e.g. like this: > > class S: > def __getitem__(self, x): return x > s = S() > > a = s[:():] > > -- > --Guido van Rossum (python.org/~guido) >
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