Porosity or accessing some variables

Hi, All:

I currently have a problem that needs to consider the position and number of particles with different sizes, so basically I am trying to calculate the porosity of the poured grains. For this target I need to know number of particles and the height of poured grains, so that I can calculate this property.

I am wondering if there is any existing examples using LIGGGHTS that can:
1. calculation of porosity
2. if there is not such a function, so how can I access (for example with python) some properties of particles after pouring

I know I can read it in dump-file but I wanted to automatize the whole procedure.

Thanks for any suggestions in advance!

Mo