Cython language_level Warning - switch to Python3?

[WillAyd]

When compiling with Cython the following warning gets issued:

Cython/Compiler/Main.py:367: FutureWarning: Cython directive 'language_level' not set, using 2 for now (Py2). This will change in a later release! File: clones/pandas/pandas/_libs/groupby.pxd

Haven't looked into the implications as of yet but probably worth switching to Python3, especially given the upcoming drop of Python2 support

[jbrockmendel]

Have you tried this locally? For me it causes python setup.py build_ext --inplace to fail

[WillAyd]

Yea it failed pretty miserably. Just for the sake of explicitness I updated the setup.py to have the following line:

directives = {'linetrace': False, 'language_level': 3}

Haven't looked in detail but assume it's an issue with how we are doing imports

[jreback]

what is next on the list for this?

[WillAyd]

I think mostly minor stuff around division differences. There’s also one fused type containing Unicode which was failing before for Py27 builds.

Most of this was wrapped up in 62bee57 - is the Py27 failure something we need to worry about after 0.24 release?

[jreback]

no issue for 0.24.0, just saw the warnings and led me here :>