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

[Gael Varoquaux]

Indeed, for scikit-learn, this would be a major problem.

Gaël

On Fri, Jun 30, 2017 at 05:55:52PM +1000, 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.

> 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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-- 
    Gael Varoquaux
    Researcher, INRIA Parietal
    NeuroSpin/CEA Saclay , Bat 145, 91191 Gif-sur-Yvette France
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    http://gael-varoquaux.info            http://twitter.com/GaelVaroquaux