Dropping support for 2.7 in 2020

[Juan Nunez-Iglesias]

I would drop 2.7 sooner. NumPy/SciPy dropping it is the absolute cutoff, but there’s no reason why we can’t jump the gun (and lead rather than follow). Py2.7 users can make do with older releases. As Stéfan mentioned, this is not about erasing Py2.7 support, but not releasing new features on Py2.7. Very different. I envision that we stop producing Py2.7 releases after 0.13, but we call that an “LTS” release which will get bugfix backports until 2020.

imho, with Py3.4 and especially Py3.5, Py3-only suddenly became very attractive. My three favourite features are type annotations, keyword-only arguments (these two together make it much easier to produce correct code and debug), and the @ matrix multiplication operator. The latter makes linear algebra code *so* *much* nicer to read and write, and we have our fair share in scikit-image. For my own projects, I am now Py3.5-only, always.

Finally, as others have mentioned, but is worth restating:
- Conda allows user-space installs of Python versions and packages, so you don’t ever depend on your sysadmin-controlled environment.
- It is *absolutely false* that conda packages are only useful on Windows — I have failed to compile scipy both on OSX and Ubuntu boxes.
- It is also *not* a requirement to download the monolithic Anaconda distro — with miniconda (which should be the default), you just install precisely what you need.
- With conda-forge we now have a community-run repository of binary conda packages.

So, in short, the switch to Py3 is easier than ever for *all* users, some might just not realise it yet ;), and switching to a Py3-only programming environment is a boon to all the scikit-image devs… though again some might not realise it yet ;).

Juan.

On 21 May 2016 at 12:20:38 PM, Nathaniel Smith (njs at vorpus.org) wrote:

On May 20, 2016 07:30, "Michael Sarahan" <msarahan at gmail.com> wrote:
> I don't think this is a concern for cython or scikit-image, but many people at bumping into the language support limit in the C++11 sense with Python 2.7 on Windows.  Since VS 2008 is the de-facto standard compiler for Python 2.7, people are unable to use C++11 code in modules for Python 2.7.  Some people use newer compilers anyway, which sometimes works, but is mixing runtimes, and can lead to bugs or crashes.  Many people would like to support Python 2.7 using a different compiler for the whole ecosystem.  One example is Ilastik, by folks at HHMI, using VS 2012 to have a custom stack: https://github.com/ilastik/ilastik-build-conda

I think getting mingwpy finished and polished is probably an easier solution for this problem than forking the entire py27-on-windows ecosystem :-)

-n

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