I needed to use the positivity constraint on the Lasso regression from scikit learn. The problem is that is not there yet in the python-sklearn package available in debian testing: it’s still stuck at 0.14.1. I don’t really want to switch to unstable for that, neither do I want to mess up my whole system by installing it manually as root.

Luckily, pip makes it easy to install as a user:

pip install -U --user scikit-learn

The whole stuff is installed in ~/.local/lib/python2.7/site-packages/sklearn and accessible from all python code without having anything special to do.