[Numpy-discussion] proposed changes to array printing in 1.14

[CJ Carey]

Is it feasible/desirable to provide a doctest runner that ignores
whitespace? That would allow downstream projects to fix their doctests on
1.14+ with a one-line change, without breaking tests on 1.13.

On Fri, Jun 30, 2017 at 11:11 AM, Allan Haldane <allanhaldane at gmail.com>
wrote:

> On 06/30/2017 03:55 AM, Juan Nunez-Iglesias wrote:
>
>> To reiterate my point on a previous thread, I don't think this should
>> happen until NumPy 2.0. This *will* break a massive number of doctests, and
>> what's worse, it will do so in a way that makes it difficult to support
>> doctesting for both 1.13 and 1.14. I don't see a big enough benefit to
>> these changes to justify breaking everyone's tests before an API-breaking
>> version bump.
>>
>
> I am still on the fence about exactly how annoying this change would be,
> and it is is good to hear whether this affects you and how badly.
>
> Yes, someone would have to spend an hour removing a hundred spaces in
> doctests, and the 1.13 to 1.14 period is trickier (but virtualenv helps).
> But none of your end users are going to have their scripts break, there are
> no new warnings or exceptions.
>
> A followup questions is, to what degree can we compromise? Would it be
> acceptable to skip the big change #1, but keep the other 3 changes? I
> expect they affect far fewer doctests. Or, for instance, I could scale back
> #1 so it only affects size-1 (or perhaps, only size-0) arrays. What amount
> of change would be OK, and how is changing a small number of doctests
> different from changing more?
>
> Also, let me clarify the motivations for the changes. As Marten noted,
> change #2 is what motivated all the other changes. Currently 0d arrays
> print in their own special way which was making it very hard to implement
> fixes to voidtype str/repr, and the datetime and other 0d reprs are weird.
> The fix is to make 0d arrays print using the same code-path as higher-d
> ndarrays, but then we ended up with reprs like "array( 1.)" because of the
> space for the sign position. So I removed the space from the sign position
> for all float arrays. But as I noted I probably could remove it for only
> size-1 or 0d arrays and still fix my problem, even though I think it might
> be pretty hacky to implement in the numpy code.
>
> Allan
>
>
>
>
>
>> On 30 Jun 2017, 6:42 AM +1000, Marten van Kerkwijk <
>> m.h.vankerkwijk at gmail.com>, wrote:
>>
>>> To add to Allan's message: point (2), the printing of 0-d arrays, is
>>> the one that is the most important in the sense that it rectifies a
>>> really strange situation, where the printing cannot be logically
>>> controlled by the same mechanism that controls >=1-d arrays (see PR).
>>>
>>> While point 3 can also be considered a bug fix, 1 & 4 are at some
>>> level matters of taste; my own reason for supporting their
>>> implementation now is that the 0-d arrays already forces me (or,
>>> specifically, astropy) to rewrite quite a few doctests, and I'd rather
>>> have everything in one go -- in this respect, it is a pity that this
>>> is separate from the earlier change in printing for structured arrays
>>> (which was also much for the better, but broke a lot of doctests).
>>>
>>> -- Marten
>>>
>>>
>>>
>>> On Thu, Jun 29, 2017 at 3:38 PM, Allan Haldane <allanhaldane at gmail.com>
>>> wrote:
>>>
>>>> Hello all,
>>>>
>>>> There are various updates to array printing in preparation for numpy
>>>> 1.14. See https://github.com/numpy/numpy/pull/9139/
>>>>
>>>> Some are quite likely to break other projects' doc-tests which expect a
>>>> particular str or repr of arrays, so I'd like to warn the list in case
>>>> anyone has opinions.
>>>>
>>>> The current proposed changes, from most to least painful by my
>>>> reckoning, are:
>>>>
>>>> 1.
>>>> For float arrays, an extra space previously used for the sign position
>>>> will now be omitted in many cases. Eg, `repr(arange(4.))` will now
>>>> return 'array([0., 1., 2., 3.])' instead of 'array([ 0., 1., 2., 3.])'.
>>>>
>>>> 2.
>>>> The printing of 0d arrays is overhauled. This is a bit finicky to
>>>> describe, please see the release note in the PR. As an example of the
>>>> effect of this, the `repr(np.array(0.))` now prints as 'array(0.)`
>>>> instead of 'array(0.0)'. Also the repr of 0d datetime arrays is now like
>>>> "array('2005-04-04', dtype='datetime64[D]')" instead of
>>>> "array(datetime.date(2005, 4, 4), dtype='datetime64[D]')".
>>>>
>>>> 3.
>>>> User-defined dtypes which did not properly implement their `repr` (and
>>>> `str`) should do so now. Otherwise it now falls back to
>>>> `object.__repr__`, which will return something ugly like
>>>> `<mytype object at 0x7f37f1b4e918>`. (Previously you could depend on
>>>> only implementing the `item` method and the repr of that would be
>>>> printed. But no longer, because this risks infinite recursions.).
>>>>
>>>> 4.
>>>> Bool arrays of size 1 with a 'True' value will now omit a space, so that
>>>> `repr(array([True]))` is now 'array([True])' instead of
>>>> 'array([ True])'.
>>>>
>>>> Allan
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