[Numpy-discussion] Output type of round is inconsistent with python built-in

[Robert Kern]

On Wed, Feb 26, 2020 at 6:59 PM <josef.pktd at gmail.com> wrote:

>
>
> On Wed, Feb 26, 2020 at 6:09 PM Robert Kern <robert.kern at gmail.com> wrote:
>
>> On Wed, Feb 26, 2020 at 5:27 PM <josef.pktd at gmail.com> wrote:
>>
>>> great another object array
>>>
>>> np.asarray([round(x_i.item()) for x_i in np.array([1, 2.5, 2e20,
>>> 2e200])])
>>> array([1, 2, 200000000000000000000,
>>>
>>>  199999999999999993946624442502072331894900655091004725296483501900693696871108151068392676809412503736055024831947764816364271468736556969278770082094479755742047182133579963622363626612334257709776896],
>>>       dtype=object)
>>>
>>>
>>> I would rather have numpy consistent with numpy than with python
>>>
>>
>> Since round() (and the __round__() interface) is part of Python and not
>> numpy, there is nothing in numpy to be consistent with. We only implement
>> __round__() for the scalar types.
>>
>
>
> Maybe I misunderstand
>
> I'm using np.round a lot. So maybe it's a question whether and how it will
> affect np.round.
>

Nope, not changing.


> Does the following change with the proposal?
>
> np.round(np.array([1, 2.5, 2e20, 2e200]))
> array([1.e+000, 2.e+000, 2.e+020, 2.e+200])
>
> np.round(np.array([1, 2.5, 2e20, 2e200])).astype(int)
> array([          1,           2, -2147483648, -2147483648])
>
> np.round(np.array([2e200])[0])
> 2e+200
>
> np.round(2e200)
> 2e+200
>

No change.


> round(2e200)
>
> 199999999999999993946624442502072331894900655091004725296483501900693696871108151068392676809412503736055024831947764816364271468736556969278770082094479755742047182133579963622363626612334257709776896
>

Obviously, not under out control, but no, that's not changing.

This is the only result that will change:

round(np.float64(2e200))
2e+200


> Josef
> "around 100" sounds like "something all_close(100)"
>

I know. It's meant to be read as "array-round". We prefer the `around()`
spelling to avoid shadowing the built-in. Early mistake that we're still
living with.

-- 
Robert Kern
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