[Wheel-builders] Questions re: scipy / skimage wheels on Windows

[Nathaniel Smith]

On Sun, Mar 20, 2016 at 2:03 PM, Stéfan van der Walt
<stefanv at berkeley.edu> wrote:
> Hi, everyone
>
> I would like to distribute scikit-image wheels on Windows.  To build
> these I require numpy and scipy, but where they come from is not too
> important.
>
> However, we have a bigger problem when it comes to users installing
> the skimage wheels, because they would also need numpy and scipy
> wheels to be available.
>
> From what I understand, we currently have the
> tools for building these onr 2.7 and 3.4, but not on 3.5.
>
> What is the latest state of things, and what is my current best course
> of action?

For scipy that's pretty much the state of things, yeah. (Or, we're on
the verge of being able to post 2.7 and 3.4 scipy wheels on Windows --
there's some tests of that happening right now on the mingwpy mailing
list.) For numpy we already have 2.7 / 3.4 / 3.5 wheels uploaded
(using somewhat-slow BLAS, but they work).

As for your best course of action, though, I don't think the
availability of numpy/scipy wheels changes anything?

For 'pip install scikit-image' to work when only an sdist is available
(the current situation), then numpy and scipy need to be already
installed (IIUC).

For 'pip install scikit-image' to to work when a wheel is available
(the hopeful future situation), then numpy and scipy need to be
either:
- available as wheels
- automatically buildable (very unlikely on windows)
- already installed

So it seems like uploading scikit-image wheels right now will only
improve the range of things that work. In particular, they'll mean
that 'pip install scikit-image' starts working usefully for people who
have already installed numpy and scipy via Gohlke's builds, or via
conda. Obviously it will be even better when scipy wheels are
available, but incremental progress is still progress :-)

I guess the one downside is that right now, if someone who is missing
the crucial things tries to do 'pip install scikit-image' then your
setup.py can give a nice error message explaining, whereas if a
scikit-image wheel is available then that person will still be doomed,
but may not get as nice an error message telling them so. (I.e.,
they'll get whatever error message you get when you try to do 'pip
install scipy' on Windows.)

-n

-- 
Nathaniel J. Smith -- https://vorpus.org