Non-standard Python on UPPMAX

This is something I’ve had to look up at least 10 times in the last year, so to save myself from searching my email inbox yet another time I will write it out here. This post is specific to the Kalkyl cluster at UPPMAX.

To make a virtual environment with Python 2.7 on UPPMAX, do the following

mkvirtualenv --no-site-packages --python=/sw/comp/python/2.7.1_kalkyl/bin/python2.7 new_venv

What’s the problem?

Firstly, the standard Python on Kalkyl is 2.6, which is incompatible with most things we do, as we all tend to use 2.7.

UPPMAX uses the module system to manage different versions of software. Naively, you would think one could make a Python 2.7 by doing

$ module load python/2.7.1
$ mkvirtualenv --no-site-packages  new_venv

This will not work.

In stead, one need to point to the Python binary as it is stored on the filesysten; the one that the module system links to when module load is called. And this is located in /sw/comp/python/2.7.1_kalkyl.