[Numpy-discussion] np.{bool,float,int} deprecation

[Aaron Meurer]

On Wed, Dec 9, 2020 at 9:41 AM Sebastian Berg
<sebastian at sipsolutions.net> wrote:
>
> On Mon, 2020-12-07 at 14:18 -0700, Aaron Meurer wrote:
> > Regarding np.bool specifically, if you want to deprecate this, you
> > might want to discuss this with us at the array API standard
> > https://github.com/data-apis/array-api (which is currently in RFC
> > stage). The spec uses bool as the name for the boolean dtype.
> >
> > Would it make sense for NumPy to change np.bool to just be the
> > boolean
> > dtype object? Unlike int and float, there is no ambiguity with bool,
> > and NumPy clearly doesn't have any issues with shadowing builtin
> > names
> > in its namespace.
>
> We could keep the Python alias around (which for `dtype=` is the same
> as `np.bool_`).
>
> I am not sure I like the idea of immediately shadowing the builtin.
> That is a switch we can avoid flipping (without warning); `np.bool_`
> and `bool` are fairly different beasts? [1]

NumPy already shadows a lot of builtins, in many cases, in ways that
are incompatible with existing ones. It's not something I would have
done personally, but it's been this way for a long time.

Aaron Meurer

> OTOH, if someone wants to entertain switching... It could be
> interesting to see how (unfixed) downstream projects react to it.
>
> One approach would be:
>
> * Go ahead for now (deprecate)
> * Add a FutureWarning at some point that we _will_ start to export
>   `np.bool` again (but `from numpy import *` is a problem?)
> * Aim to make `np.bool is np.bool_` at some point in the (far) future.
>
> It is multi-step (and I recall opinions that multi-step is bad).
> Although, I think the main argument against it was to not force users
> to modify code more than once.  And I do not think that happens here.
>
> Of course we could use the `FutureWarning` right away, but I don't mind
> taking it slow.
>
> Cheers,
>
> Sebastian
>
>
>
> [1] I admit, probably almost nobody would notice. And usually using a
> Python `bool` is better...
>
>
> >
> > Aaron Meurer
> >
> > On Sat, Dec 5, 2020 at 4:31 PM Juan Nunez-Iglesias <jni at fastmail.com>
> > wrote:
> > > Hi all,
> > >
> > > At the prodding [1] of Sebastian, I’m starting a discussion on the
> > > decision to deprecate np.{bool,float,int}. This deprecation broke
> > > our prerelease testing in scikit-image (which, hooray for rcs!),
> > > and resulted in a large amount of code churn to fix [2].
> > >
> > > To be honest, I do think *some* sort of deprecation is needed,
> > > because for the longest time I thought that np.float was what
> > > np.float_ actually is. I think it would be worthwhile to move to
> > > *that*, though it’s an even more invasive deprecation than the
> > > currently proposed one. Writing `x = np.zeros(5, dtype=int)` is
> > > somewhat magical, because someone with a strict typing mindset
> > > (there’s an increasing number!) might expect that this is an array
> > > of pointers to Python ints. This is why I’ve always preferred to
> > > write `dtype=np.int`, resulting in the current code churn.
> > >
> > > I don’t know what the best answer is, just sparking the discussion
> > > Sebastian wants to see. ;) For skimage we’ve already merged a fix
> > > (even if it is one of dubious quality, as Stéfan points out [3] ;),
> > > so I don’t have too much stake in the outcome.
> > >
> > > Juan.
> > >
> > > [1]:
> > > https://github.com/scikit-image/scikit-image/pull/5103#issuecomment-739334463
> > > [2]: https://github.com/scikit-image/scikit-image/pull/5103
> > > [3]:
> > > https://github.com/scikit-image/scikit-image/pull/5103#issuecomment-739368765
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