[Numpy-discussion] ndrange, like range but multidimensiontal
mark.harfouche at gmail.com
Thu Oct 11 21:53:53 EDT 2018
Eric, interesting ideas.
> __getitem__(Tuple[int]) which returns numpy scalars
I'm not sure what you mean. Even if you supply a numpy uint8 to range, it
still returns a python int class.
Would you like ndrange to return a tuple of `uint8` in this case?
In : a =
Ravel seems like a cool way to choose iteration order. In the PR, I
mentionned that one reason that I removed `'F'` order from the PR was:
1. My implementation was not competitive with the `C` order implementation
in terms of speed (can be fixed)
2. I don't know if it something that people really need to iterate over
collections (annoying to maintain if unused)
Instead, I just showed an example how people could iterate in `F` order
should they need to.
I'm not sure if we ever want the `ndrange` object to return a full matrix.
It seems like we would be creating a custom tuple class just for this which
seems pretty niche.
On Thu, Oct 11, 2018 at 10:21 AM Eric Wieser <wieser.eric+numpy at gmail.com>
> Isn’t that what arange is for?
> Imagining ourselves in python2 land for now - I’m proposing arange is to
> range, as ndrange is to xrange
> I’m not convinced it should return an ndarray
> I agree - I think it should return a range-like object that:
> - Is convertible via __array__ if needed
> - Looks like an ndarray, with:
> - a .dtype attribute
> - a __getitem__(Tuple[int]) which returns numpy scalars
> - .ravel() and .flat for choosing iteration order.
> On Wed, 10 Oct 2018 at 11:21 Allan Haldane allanhaldane at gmail.com
> <http://mailto:email@example.com> wrote:
> On 10/10/18 12:34 AM, Eric Wieser wrote:
>> > One thing that worries me here - in python, |range(...)| in essence
>> > generates a lazy |list| - so I’d expect |ndrange| to generate a lazy
>> > |ndarray|. In practice, that means it would be a duck-type defining an
>> > |__array__| method to evaluate it, and only implement methods already
>> > present in numpy.
>> Isn't that what arange is for?
>> It seems like there are two uses of python3's range: 1. creating a 1d
>> iterable of indices for use in for-loops, and 2. with list(range) can be
>> used to create a sequence of integers.
>> Numpy can extend this in two directions:
>> * ndrange returns an iterable of nd indices (for for-loops).
>> * arange returns an 1d ndarray of integers instead of a list
>> The application of for-loops, which is more niche, doesn't need
>> ndarray's vectorized properties, so I'm not convinced it should return
>> an ndarray. It certainly seems simpler not to return an ndarray, due to
>> the dtype question.
>> arange on its own seems to cover the need for a vectorized version of
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