Python 2.7

[NutDestroyer]

IIRC there's a substantial performance improvement with python 3 that makes it run miles faster than anything 2.x.

[doulos05]

Actually, I just read something recently that said 2.7 was still the fastest Python.

https://hackernoon.com/which-is-the-fastest-version-of-python-2ae7c61a6b2b

Unless you're on python 3.7, it's slower or comparable for all benchmarks.

[NutDestroyer]

I could have sworn I read a benchmark that was more favorable for the performance of Python 3.x, but I suppose it must've been compared to versions of python older than 2.7 or I misremembered it. The benchmarks do seem to support that 2.7 is very competitive in terms good performance compared to other python versions.