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

[Juan Nunez-Iglesias]

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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