Dropping support for 2.7 in 2020

[Thomas Kluyver]

I'd like to revive this discussion with a bit of added context. We 
(principally people from IPython/Jupyter, Matplotlib, Sympy and Scikit-bio) 
are putting together a statement for Scientific Python community projects 
to signal that we're not planning to maintain Python 2 support forever. 
We're saying that we will end Python 2 support in or before 2020, to 
correspond with the end of support for Python 2.7 itself.

http://python3statement.github.io/

The more projects that get on board with this, the better we can make the 
case that researchers and users need Python 3 to be available. Then we can 
all benefit from a reduced maintenance burden. So scikit-image wouldn't be 
making a lone stand on this - there are a number of projects already 
agreeing to drop Python 2 support by 2020, and we hope there will be more 
soon.

Thanks,
Thomas

On Monday, 23 May 2016 04:30:21 UTC+1, Juan Nunez-Iglesias wrote:
>
> 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 (n... at vorpus.org 
> <javascript:>) wrote:
>
> On May 20, 2016 07:30, "Michael Sarahan" <msar... at gmail.com <javascript:>> 
> 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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