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

Allan Haldane allanhaldane at gmail.com
Fri Jun 30 15:36:59 EDT 2017


On 06/30/2017 03:04 PM, CJ Carey wrote:
> 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.

Good idea. I have already implemented this actually, see the updated PR.
https://github.com/numpy/numpy/pull/9139/

Whether or not the sign position is padded can now be controlled by setting

    >>> np.set_printoptions(pad_sign=True)
    >>> np.set_printoptions(pad_sign=False)

When pad_sign is True, it gives the old behavior, except for size-1
arrays where it still omits the sign position. (Maybe I should limit it
even more, to 0d arrays?)

When pad_sign is False (currently default in the PR), it removes the
sign padding everywhere if possible.

Allan



> 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
>>>>> _______________________________________________
>>>>> NumPy-Discussion mailing list
>>>>> NumPy-Discussion at python.org
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>>>>>
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