[Numpy-discussion] Deprecate matrices in 1.15 and remove in 1.17?

[Stefan van der Walt]

On Thu, Nov 30, 2017, at 16:15, Nathaniel Smith wrote:
> PendingDeprecationWarning in np.matrix.__init__ (unless it kills
> performance for scikit-learn and friends), and put a big warning box
> at the top of the docs. The idea here is to not actually break
> anyone's code, but start to get out the message that we definitely
> don't think anyone should use this if they have any alternative.
> 
> - After there's an alternative to scipy.sparse: ramp up the warnings,
> possibly all the way to FutureWarning so that existing scripts don't
> break but they do get noisy warnings
> 
> - Eventually, if we think it will reduce maintenance costs: split it
> into a subpackage

Can't we make `np.matrix` into a new package right now, and have NumPy
depend on it internally?  At that point, start warning users that they
should also be using the external package, and eventually just remove
the shim in NumPy.

Stéfan