Pause/Resume simulation

[maxfischer2781]

Short description of the feature
Allow to pause the simulation and later on resume it.

Describe the solution you'd like
Simulation code should be able to pause at any time. This freezes the current simulation state.

async def some_activity():
     if time == 20:
        await usim.resume  # new call to pause simulation until resumed

Each simulation is represented by an object. usim.run returns this object when the simulation is frozen. The object allows unfreezing:

simulation = usim.run(some_activity())
print("Current state:", simulation)
simulation.resume()

Describe alternatives and the context you have considered
There is currently no way to freeze a simulation.

[karstenle]

(Thanks for the work @maxfischer2781)

This would also allow to create functions to run a simulation step by step.

async def _step_activity():
     while True:
        await usim.resume 
        await (time + 1)

def run_in_steps(*activities):
      return usim.run(_step_activity(), *activities)

def step(simulation):
     simulation.resume()

and then use it via

simulation = run_in_steps(*some_activities)
for i in range(100):
     step(simulation)