List of lists...of lists (python)

I'm attempting to make a rogue-like dungeon generator in python. I'm pretty sure everything I'm doing is terrible, but if it works, I'm happy.

Anyways, I have a list of lists of lists. How would I be able to get to the creamy nueget center of my lists? I've only done this type of thing in Scheme which basically consisted of (first (first (first lst))). How do I do this in python?