Migration to Python 3.x

[Juan Nunez-Iglesias]

Hi everyone,

First of all, I excitedly jumped on the bandwagon because Stefan mentioned
0.13, but I actually even I considered that a bit early for dropping Py2
when I read it. =) I would say that the right time to drop Py2 is either
0.15 or 1.0, and that we should follow a standard deprecation cycle. What
this means is some warning (on the home page, or on installation, for
example) that as of version <foo>.<bar>, scikit-image will be Python
3-only, with the previous release being an LTS release with Python 2
support.

An important corollary to this thread is signing the Python 3 statement
<https://python3statement.github.io/>, which pledges dropping Python 2
support by **2020**. We can commit to a longer timeline than envisioned by
Stéfan's initial proposal, but I would like to commit to a timeline,
because I think having the scikit-image logo on that page would definitely
add momentum to the transition. Which it (cough) clearly needs.

As Stéfan has noted, Ubuntu users haven't had 0.12 in the package manager
in ages and the sky hasn't fallen. A long-term support release is *not* the
same as abandoning our users. I would find it much less burdensome to
backport certain bug fixes and critical features to 0.13.25 (or whatever)
than to keep supporting 2.7 ad infinitum. The deprecation cycle in
particular just bugs the hell out of me.

About the benefits of switching, Johannes, although you argue that Python3
doesn't make the code "more correct", this is not strictly the case:
keyword-only arguments, better readability (with @), and typing, *all* make
it easier to avoid bugs. You can hardly claim that skimage is bug-free.
I'll note that in my own project, gala, a user discovered a monster bug
that will result in me issuing a correction to the paper:
https://github.com/janelia-flyem/gala/issues/63
Both typing and keyword-only arguments would have prevented this bug.

Emma, thank you so much for those statistics. They are so valuable. =) I
agree *a lot* about outreach + docs, and growing our user base. But I think
all those efforts should focus on Python 3 anyway.

So anyway, I hope I've added some fuel to the fire with my bug disaster,
above. =) And I hope we can agree on a timeline, even if the timeline is
not quite as aggressive as Jupyter's or Stéfan's original proposal.

Thanks all!

Juan.

On Thu, Aug 11, 2016 at 8:24 AM, Stéfan van der Walt <stefanv at berkeley.edu>
wrote:

> On 10 August 2016 at 01:03, Emmanuelle Gouillart <
> emmanuelle.gouillart at nsup.org> wrote:
>
>> I completely agree that it would be great to obtain statistics about
>> who uses Python 2.7 or 3.x but I can't see an easy way to do it. Could we
>> have a button on the website linking to a small form asking whether
>> people are using Python 2.7 or 3.x? Maybe it has already been mentioned
>> on the mailing-list.
>>
>
> I'll work on getting hold of some statistics from PyPA.
>
>
>> 2) so, to estimate when the change should happen (0.14, 0.15?), we need
>> to evaluate the "economics" of such a decision. How many users are going
>> to be impacted? How much development time are we losing by not switching
>> right now? How do we balance these two factors (or others)?
>>
>
> I don't think the developer cost is very high right now.  I wanted to test
> the waters a bit and see how the rest of the team felt, but I think there
> are enough compelling arguments to stick to 2.7-compatibility for now.  We
> can always revisit the issue again a year or so from now, when the
> landscape might have changed.
>
> Thanks for all the feedback!
>
> Stéfan
>
> --
> You received this message because you are subscribed to the Google Groups
> "scikit-image" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to scikit-image+unsubscribe at googlegroups.com.
> To post to this group, send email to scikit-image at googlegroups.com.
> To view this discussion on the web, visit https://groups.google.com/d/
> msgid/scikit-image/CABDkGQ%3DEzzSY1j9qy%2BD3VkzVP4zeHknBrqkBZ%3D9m7Q_
> H4qSvCA%40mail.gmail.com
> <https://groups.google.com/d/msgid/scikit-image/CABDkGQ%3DEzzSY1j9qy%2BD3VkzVP4zeHknBrqkBZ%3D9m7Q_H4qSvCA%40mail.gmail.com?utm_medium=email&utm_source=footer>
> .
>
> For more options, visit https://groups.google.com/d/optout.
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/scikit-image/attachments/20160811/5c8e85a5/attachment.html>