It's fine for square widths of around 20 cells, but when you 200 it slows right down.

It appears to be caused by the line agent.random.choice(sorted(self.empties)) where it sorts the empties first. I guess it does this so you can replicate the results using random seed?

If you don't care about replication however, it's unreasonably slow and can be fixed by using agent.random.choice(list(self.empties)) instead (speeding it enormously).

I'm not sure of the design decisions here, but maybe it's worth having two functions to make it clear or passing some sort of bool?

https://mesa.readthedocs.io/en/stable/mesa.html#mesa.space.SingleGrid.position_agent