poohsticks.py

import simpy
import random

a, b, c = 10, 30, 5
strict = +1 # +1 for version A, -1 for version B

def lap(sim, event):
    laps[event.data] = strict * event.priority
    if abs(laps[0] - laps[1]) > 1:
        sim.stop_at(event.time)
    sim.publish(simpy.Event(event.time + c + random.randint(a, b),
                            event.priority + strict, '', event.data))

laps = [0, 0]
sim = simpy.Simulation()
sim.subscribe('', lap)
for player in range(2):
    sim.publish(simpy.Event(random.randint(a, b), 0, '', player))
sim.run()