SimPy is a process-based discrete-event simulation language based on standard Python and released under the GNU LGPL.
It provides the modeller with components of a simulation model. These include processes, for active components like customers, messages, and vehicles, and resources, for passive components that form limited capacity congestion points like servers, checkout counters, and tunnels. It also provides monitor variables to aid in gathering statistics.
More information can be obtained from the SimPy Homepage: http://simpy.readthedocs.org/