simpy.rt — Real-time simulation

Execution environment for events that synchronizes passing of time with the real-time (aka wall-clock time).

class simpy.rt.RealtimeEnvironment(initial_time=0, factor=1.0, strict=True)

Execution environment for an event-based simulation which is synchronized with the real-time (also known as wall-clock time). A time step will take factor seconds of real time (one second by default). A step from 0 to 3 with a factor=0.5 will, for example, take at least 1.5 seconds.

The step() method will raise a RuntimeError if a time step took too long to compute. This behaviour can be disabled by setting strict to False.


The current simulation time.


The currently active process of the environment.


Scaling factor of the real-time.


Running mode of the environment. step() will raise a RuntimeError if this is set to True and the processing of events takes too long.


Create a new Process instance for generator.

timeout(delay, value=None)

Return a new Timeout event with a delay and, optionally, a value.


Return a new Event instance. Yielding this event suspends a process until another process triggers the event.


Return a new AllOf condition for a list of events.


Return a new AnyOf condition for a list of events.


Stop the current process, optionally providing a value.

This is a convenience function provided for Python versions prior to 3.3. From Python 3.3, you can instead use return value in a process.

schedule(event, priority=1, delay=0)

Schedule an event with a given priority and a delay.


Get the time of the next scheduled event. Return Infinity if there is no further event.


Process the next event after enough real-time has passed for the event to happen.

The delay is scaled according to the real-time factor. With strict mode enabled, a RuntimeError will be raised, if the event is processed too slowly.


Synchronize the internal time with the current wall-clock time.

This can be useful to prevent step() from raising an error if a lot of time passes between creating the RealtimeEnvironment and calling run() or step().


Executes step() until the given criterion until is met.

  • If it is None (which is the default), this method will return when there are no further events to be processed.
  • If it is an Event, the method will continue stepping until this event has been triggered and will return its value. Raises a RuntimeError if there are no further events to be processed and the until event was not triggered.
  • If it is a number, the method will continue stepping until the environment’s time reaches until.