Add slicing support for ellipsis and None

[mrocklin]

I ran into this while testing https://github.com/mrocklin/sparse/pull/35 .

@hameerabbasi if you have a moment to look this over I would welcome your review

[hameerabbasi]

Looks great to me. One minor point: A check to see there isn't more than one Ellipsis and a subsequent exception + test for that exception would be great. Either way, it doesn't block previous use cases, so should be good to merge.

Edit: Ideally, the exception should be IndexError: an index can only have a single ellipsis ('...') to match Numpy behavior.

[mrocklin]

Added such a test. It looks like Python handles this check for us.

[mrocklin]

Ah, never mind. My test was faulty here

[hameerabbasi]

There is a spelling error here. sllipsis should be Ellipsis.

[mrocklin]

Thanks. Fixed

…

On Sun, Dec 24, 2017 at 8:42 AM, Hameer Abbasi ***@***.***> wrote: ***@***.**** commented on this pull request. ------------------------------ In sparse/core.py <https://github.com/mrocklin/sparse/pull/37#discussion_r158605898>: > @@ -233,10 +233,19 @@ def __sizeof__(self): def __getitem__(self, index): if not isinstance(index, tuple): index = (index,) - index = tuple(ind + self.shape[i] if isinstance(ind, numbers.Integral) and ind < 0 else ind + if len(index) - index.count(None) > self.ndim: + raise IndexError("too many indices for array") + if index.count(Ellipsis) > 1: + raise IndexError("an index can only have a single sllipsis ('...')") There is a spelling error here. sllipsis should be Ellipsis. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <https://github.com/mrocklin/sparse/pull/37#pullrequestreview-85445245>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AASszMWNg0ryroKdK3h2tKt7HzJT9hiKks5tDn7agaJpZM4RLtHw> .

[hameerabbasi]

This will fail on things like a[1, ...] where a is (n,)-shaped. There should be an additional factor of - index.count(Ellipsis) here.

[hameerabbasi]

Sorry for requesting so much changes. Here's the last one. It's nitpicky, sure, but I want to make sure all our bases are covered.

[mrocklin]

Sorry for requesting so much changes. Here's the last one. It's nitpicky, sure, but I want to make sure all our bases are covered.

No, this is great. Thank you for all of your work reviewing here.

[hameerabbasi]

I may be missing something here, but won't np.array([]) create an array with a dtype of float64 and a shape of (0,)? It would be much nicer to do this: coords = np.empty((len(shape), 0), dtype=np.uint8)

[hameerabbasi]

And also to specify a dtype even in the first case, as for empty arrays it might also be float64. np.result_type and np.min_scalar_type should be useful here.

[hameerabbasi]

Some minor comments that will hopefully address the CI failures.