I am writing a driver script for my reactor model that defines things like fuel conditions, rod heights, sim settings, ect. I want the driver script to be the only script that needs to be edited and run in order for the model to function. I’m caught up on the fuel lattice definition. I would like to be able to describe the lattice (locations of different types of elements) within the input script and have that be read into the main script where the element universes and the lattice itself is defined. However, the element universes are not defined in the driver script, nor can they be without creating an infinite loop. Does anyone have a way of passing a matrix variable into the main openmc python script and have it converted into a corresponding lattice with the actual element universes inserted?