Please provide example usage for PyDOS and Python 3 support

[dburkhardt]

This is a great tool! I'm working on a project where we need to estimate the density of eigenvalues of a large Laplacian matrix. Reading your paper, this looks like a useful way to speed up our computations. If it works, eventually we'd like to include this in a package my lab is developing for biomedical data analysis over at https://github.com/krishnaswamylab/MELD.

To test this though, it would be really helpful if you could please provide example usage for the Python implementation. I am currently going through the tests files, but example usage for a simple case would be helpful.

Also, before we can include this in our package, we really will need a Python 3 implementation. We can cross that bridge later, but with Python 2 losing support this year, we need to stick to Python 3.

Thanks for your great work!
-Dan

[Chen-Cai-OSU]

Totally agree. I think python 3 support will make this paper much more impactful.