SimPy is a process-based discrete-event simulation framework in Python (simpy.readthedocs.io)

I discovered it in the Twins BFT project and it seems very useful to simulate distributed systems

I've used Simpy for a number of client projects at a Big 4 firm in their consulting division. Projects covered a range of simulations across Mining, Agriculture, Justice, Healthcare and a couple others.

Mainly was simulating how things flow through a network - whether that is physical or process based.