simpy.core — SimPy’s core components

Core components for event-discrete simulation environments.

class simpy.core.Environment(initial_time: int | float = 0)

Execution environment for an event-based simulation. The passing of time is simulated by stepping from event to event.

You can provide an initial_time for the environment. By default, it starts at 0.

This class also provides aliases for common event types, for example process, timeout and event.

property now: int | float

The current simulation time.

property active_process: Process | None

The currently active process of the environment.


alias of Process


alias of Timeout


alias of Event


alias of AllOf


alias of AnyOf

schedule(event: Event, priority: EventPriority = 1, delay: int | float = 0) None

Schedule an event with a given priority and a delay.

peek() int | float

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

step() None

Process the next event.

Raise an EmptySchedule if no further events are available.

run(until: int | float | Event | None = None) Any | None

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.

class simpy.core.BoundClass(cls: Type[T])

Allows classes to behave like methods.

The __get__() descriptor is basically identical to function.__get__() and binds the first argument of the cls to the descriptor instance.

static bind_early(instance: object) None

Bind all BoundClass attributes of the instance’s class to the instance itself to increase performance.

class simpy.core.EmptySchedule

Thrown by an Environment if there are no further events to be processed.

simpy.core.Infinity: float = inf

Convenience alias for infinity