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

[Allan Haldane]

On 06/30/2017 09:17 AM, Gael Varoquaux wrote:
> Indeed, for scikit-learn, this would be a major problem.
> 
> Gaël

I just ran the scikit-learn tests.

With the new behavior (removed whitespace), I do get 70 total failures:

    $ make test-doc
    Ran 39 tests in 39.503s
    FAILED (SKIP=3, failures=19)

    $ make test
    Ran 8122 tests in 387.650s
    FAILED (SKIP=58, failures=51)

After setting `np.set_printoptions(pad_sign=True)` (see other email) I
get only 1 failure in total, which is due to the presence of a 0d array
in gaussian_process.rst.

So it looks like the pad_sign option as currently implemented is good
enough to avoid almost all doctest errors.

Allan



> 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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