# `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.

  process

    alias of `Process`

  timeout

    alias of `Timeout`

  event

    alias of `Event`

  all_of

    alias of `AllOf`

  any_of

    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