`simpy.events` — Core event types¶

This module contains the basic event types used in SimPy.

The base class for all events is Event. Though it can be directly used, there are several specialized subclasses of it.

`Event`(env)	An event that may happen at some point in time.
`Timeout`(env, delay[, value])	A `Event` that gets triggered after a delay has passed.
`Process`(env, generator)	Process an event yielding generator.
`AnyOf`(env, events)	A `Condition` event that is triggered if any of a list of events has been successfully triggered.
`AllOf`(env, events)	A `Condition` event that is triggered if all of a list of events have been successfully triggered.

This module also defines the Interrupt exception.

simpy.events.PENDING = object()¶: Unique object to identify pending values of events.

simpy.events.URGENT = 0¶: Priority of interrupts and process initialization events.

simpy.events.NORMAL = 1¶: Default priority used by events.

class simpy.events.Event(env)¶

An event that may happen at some point in time.

An event

may happen (triggered is False),
is going to happen (triggered is True) or
has happened (processed is True).

Every event is bound to an environment env and is initially not triggered. Events are scheduled for processing by the environment after they are triggered by either succeed(), fail() or trigger(). These methods also set the ok flag and the value of the event.

An event has a list of callbacks. A callback can be any callable. Once an event gets processed, all callbacks will be invoked with the event as the single argument. Callbacks can check if the event was successful by examining ok and do further processing with the value it has produced.

Failed events are never silently ignored and will raise an exception upon being processed. If a callback handles an exception, it must set defused to True to prevent this.

This class also implements __and__() (&) and __or__() (|). If you concatenate two events using one of these operators, a Condition event is generated that lets you wait for both or one of them.

env = None¶: The Environment the event lives in.

callbacks = None¶: List of functions that are called when the event is processed.

triggered¶: Becomes True if the event has been triggered and its callbacks are about to be invoked.

processed¶: Becomes True if the event has been processed (e.g., its callbacks have been invoked).

ok¶

Becomes True when the event has been triggered successfully.

A “successful” event is one triggered with succeed().

Raises:	AttributeError – if accessed before the event is triggered.

defused¶

Becomes True when the failed event’s exception is “defused”.

When an event fails (i.e. with fail()), the failed event’s value is an exception that will be re-raised when the Environment processes the event (i.e. in step()).

It is also possible for the failed event’s exception to be defused by setting defused to True from an event callback. Doing so prevents the event’s exception from being re-raised when the event is processed by the Environment.

value¶

The value of the event if it is available.

The value is available when the event has been triggered.

Raises AttributeError if the value is not yet available.

trigger(event)¶

Trigger the event with the state and value of the provided event. Return self (this event instance).

This method can be used directly as a callback function to trigger chain reactions.

succeed(value=None)¶

Set the event’s value, mark it as successful and schedule it for processing by the environment. Returns the event instance.

Raises RuntimeError if this event has already been triggerd.

fail(exception)¶

Set exception as the events value, mark it as failed and schedule it for processing by the environment. Returns the event instance.

Raises ValueError if exception is not an Exception.

Raises RuntimeError if this event has already been triggered.

class simpy.events.Timeout(env, delay, value=None)¶

A Event that gets triggered after a delay has passed.

This event is automatically triggered when it is created.

defused¶

Becomes True when the failed event’s exception is “defused”.

When an event fails (i.e. with fail()), the failed event’s value is an exception that will be re-raised when the Environment processes the event (i.e. in step()).

It is also possible for the failed event’s exception to be defused by setting defused to True from an event callback. Doing so prevents the event’s exception from being re-raised when the event is processed by the Environment.

fail(exception)¶

Set exception as the events value, mark it as failed and schedule it for processing by the environment. Returns the event instance.

Raises ValueError if exception is not an Exception.

Raises RuntimeError if this event has already been triggered.

ok¶

Becomes True when the event has been triggered successfully.

A “successful” event is one triggered with succeed().

Raises:	AttributeError – if accessed before the event is triggered.

processed¶: Becomes True if the event has been processed (e.g., its callbacks have been invoked).

succeed(value=None)¶

Set the event’s value, mark it as successful and schedule it for processing by the environment. Returns the event instance.

Raises RuntimeError if this event has already been triggerd.

trigger(event)¶

Trigger the event with the state and value of the provided event. Return self (this event instance).

This method can be used directly as a callback function to trigger chain reactions.

triggered¶: Becomes True if the event has been triggered and its callbacks are about to be invoked.

value¶

The value of the event if it is available.

The value is available when the event has been triggered.

Raises AttributeError if the value is not yet available.

class simpy.events.Initialize(env, process)¶

Initializes a process. Only used internally by Process.

This event is automatically triggered when it is created.

defused¶

Becomes True when the failed event’s exception is “defused”.

When an event fails (i.e. with fail()), the failed event’s value is an exception that will be re-raised when the Environment processes the event (i.e. in step()).

It is also possible for the failed event’s exception to be defused by setting defused to True from an event callback. Doing so prevents the event’s exception from being re-raised when the event is processed by the Environment.

fail(exception)¶

Set exception as the events value, mark it as failed and schedule it for processing by the environment. Returns the event instance.

Raises ValueError if exception is not an Exception.

Raises RuntimeError if this event has already been triggered.

ok¶

Becomes True when the event has been triggered successfully.

A “successful” event is one triggered with succeed().

Raises:	AttributeError – if accessed before the event is triggered.

processed¶: Becomes True if the event has been processed (e.g., its callbacks have been invoked).

succeed(value=None)¶

Set the event’s value, mark it as successful and schedule it for processing by the environment. Returns the event instance.

Raises RuntimeError if this event has already been triggerd.

trigger(event)¶

Trigger the event with the state and value of the provided event. Return self (this event instance).

This method can be used directly as a callback function to trigger chain reactions.

triggered¶: Becomes True if the event has been triggered and its callbacks are about to be invoked.

value¶

The value of the event if it is available.

The value is available when the event has been triggered.

Raises AttributeError if the value is not yet available.

class simpy.events.Interruption(process, cause)¶

Immediately schedules an Interrupt exception with the given cause to be thrown into process.

This event is automatically triggered when it is created.

defused¶

Becomes True when the failed event’s exception is “defused”.

When an event fails (i.e. with fail()), the failed event’s value is an exception that will be re-raised when the Environment processes the event (i.e. in step()).

It is also possible for the failed event’s exception to be defused by setting defused to True from an event callback. Doing so prevents the event’s exception from being re-raised when the event is processed by the Environment.

fail(exception)¶

Set exception as the events value, mark it as failed and schedule it for processing by the environment. Returns the event instance.

Raises ValueError if exception is not an Exception.

Raises RuntimeError if this event has already been triggered.

ok¶

Becomes True when the event has been triggered successfully.

A “successful” event is one triggered with succeed().

Raises:	AttributeError – if accessed before the event is triggered.

processed¶: Becomes True if the event has been processed (e.g., its callbacks have been invoked).

succeed(value=None)¶

Set the event’s value, mark it as successful and schedule it for processing by the environment. Returns the event instance.

Raises RuntimeError if this event has already been triggerd.

trigger(event)¶

Trigger the event with the state and value of the provided event. Return self (this event instance).

This method can be used directly as a callback function to trigger chain reactions.

triggered¶: Becomes True if the event has been triggered and its callbacks are about to be invoked.

value¶

The value of the event if it is available.

The value is available when the event has been triggered.

Raises AttributeError if the value is not yet available.

class simpy.events.Process(env, generator)¶

Process an event yielding generator.

A generator (also known as a coroutine) can suspend its execution by yielding an event. Process will take care of resuming the generator with the value of that event once it has happened. The exception of failed events is thrown into the generator.

Process itself is an event, too. It is triggered, once the generator returns or raises an exception. The value of the process is the return value of the generator or the exception, respectively.

Note

Python version prior to 3.3 do not support return statements in generators. You can use :meth:~simpy.core.Environment.exit() as a workaround.

Processes can be interrupted during their execution by interrupt().

target¶

The event that the process is currently waiting for.

Returns None if the process is dead or it is currently being interrupted.

is_alive¶: True until the process generator exits.

interrupt(cause=None)¶

Interupt this process optionally providing a cause.

A process cannot be interrupted if it already terminated. A process can also not interrupt itself. Raise a RuntimeError in these cases.

defused¶

Becomes True when the failed event’s exception is “defused”.

When an event fails (i.e. with fail()), the failed event’s value is an exception that will be re-raised when the Environment processes the event (i.e. in step()).

It is also possible for the failed event’s exception to be defused by setting defused to True from an event callback. Doing so prevents the event’s exception from being re-raised when the event is processed by the Environment.

fail(exception)¶

Set exception as the events value, mark it as failed and schedule it for processing by the environment. Returns the event instance.

Raises ValueError if exception is not an Exception.

Raises RuntimeError if this event has already been triggered.

ok¶

Becomes True when the event has been triggered successfully.

A “successful” event is one triggered with succeed().

Raises:	AttributeError – if accessed before the event is triggered.

processed¶: Becomes True if the event has been processed (e.g., its callbacks have been invoked).

succeed(value=None)¶

Set the event’s value, mark it as successful and schedule it for processing by the environment. Returns the event instance.

Raises RuntimeError if this event has already been triggerd.

trigger(event)¶

Trigger the event with the state and value of the provided event. Return self (this event instance).

This method can be used directly as a callback function to trigger chain reactions.

triggered¶: Becomes True if the event has been triggered and its callbacks are about to be invoked.

value¶

The value of the event if it is available.

The value is available when the event has been triggered.

Raises AttributeError if the value is not yet available.

class simpy.events.Condition(env, evaluate, events)¶

An event that gets triggered once the condition function evaluate returns True on the given list of events.

The value of the condition event is an instance of ConditionValue which allows convenient access to the input events and their values. The ConditionValue will only contain entries for those events that occurred before the condition is processed.

If one of the events fails, the condition also fails and forwards the exception of the failing event.

The evaluate function receives the list of target events and the number of processed events in this list: evaluate(events, processed_count). If it returns True, the condition is triggered. The Condition.all_events() and Condition.any_events() functions are used to implement and (&) and or (|) for events.

Condition events can be nested.

static all_events(events, count)¶: An evaluation function that returns True if all events have been triggered.

static any_events(events, count)¶: An evaluation function that returns True if at least one of events has been triggered.

defused¶

Becomes True when the failed event’s exception is “defused”.

When an event fails (i.e. with fail()), the failed event’s value is an exception that will be re-raised when the Environment processes the event (i.e. in step()).

It is also possible for the failed event’s exception to be defused by setting defused to True from an event callback. Doing so prevents the event’s exception from being re-raised when the event is processed by the Environment.

fail(exception)¶

Set exception as the events value, mark it as failed and schedule it for processing by the environment. Returns the event instance.

Raises ValueError if exception is not an Exception.

Raises RuntimeError if this event has already been triggered.

ok¶

Becomes True when the event has been triggered successfully.

A “successful” event is one triggered with succeed().

Raises:	AttributeError – if accessed before the event is triggered.

processed¶: Becomes True if the event has been processed (e.g., its callbacks have been invoked).

succeed(value=None)¶

Set the event’s value, mark it as successful and schedule it for processing by the environment. Returns the event instance.

Raises RuntimeError if this event has already been triggerd.

trigger(event)¶

Trigger the event with the state and value of the provided event. Return self (this event instance).

This method can be used directly as a callback function to trigger chain reactions.

triggered¶: Becomes True if the event has been triggered and its callbacks are about to be invoked.

value¶

The value of the event if it is available.

The value is available when the event has been triggered.

Raises AttributeError if the value is not yet available.

class simpy.events.AllOf(env, events)¶

A Condition event that is triggered if all of a list of events have been successfully triggered. Fails immediately if any of events failed.

defused¶

Becomes True when the failed event’s exception is “defused”.

When an event fails (i.e. with fail()), the failed event’s value is an exception that will be re-raised when the Environment processes the event (i.e. in step()).

It is also possible for the failed event’s exception to be defused by setting defused to True from an event callback. Doing so prevents the event’s exception from being re-raised when the event is processed by the Environment.

fail(exception)¶

Set exception as the events value, mark it as failed and schedule it for processing by the environment. Returns the event instance.

Raises ValueError if exception is not an Exception.

Raises RuntimeError if this event has already been triggered.

ok¶

Becomes True when the event has been triggered successfully.

A “successful” event is one triggered with succeed().

Raises:	AttributeError – if accessed before the event is triggered.

processed¶: Becomes True if the event has been processed (e.g., its callbacks have been invoked).

succeed(value=None)¶

Set the event’s value, mark it as successful and schedule it for processing by the environment. Returns the event instance.

Raises RuntimeError if this event has already been triggerd.

trigger(event)¶

Trigger the event with the state and value of the provided event. Return self (this event instance).

This method can be used directly as a callback function to trigger chain reactions.

triggered¶: Becomes True if the event has been triggered and its callbacks are about to be invoked.

value¶

The value of the event if it is available.

The value is available when the event has been triggered.

Raises AttributeError if the value is not yet available.

class simpy.events.AnyOf(env, events)¶

A Condition event that is triggered if any of a list of events has been successfully triggered. Fails immediately if any of events failed.

defused¶

Becomes True when the failed event’s exception is “defused”.

When an event fails (i.e. with fail()), the failed event’s value is an exception that will be re-raised when the Environment processes the event (i.e. in step()).

It is also possible for the failed event’s exception to be defused by setting defused to True from an event callback. Doing so prevents the event’s exception from being re-raised when the event is processed by the Environment.

fail(exception)¶

Set exception as the events value, mark it as failed and schedule it for processing by the environment. Returns the event instance.

Raises ValueError if exception is not an Exception.

Raises RuntimeError if this event has already been triggered.

ok¶

Becomes True when the event has been triggered successfully.

A “successful” event is one triggered with succeed().

Raises:	AttributeError – if accessed before the event is triggered.

processed¶: Becomes True if the event has been processed (e.g., its callbacks have been invoked).

succeed(value=None)¶

Set the event’s value, mark it as successful and schedule it for processing by the environment. Returns the event instance.

Raises RuntimeError if this event has already been triggerd.

trigger(event)¶

Trigger the event with the state and value of the provided event. Return self (this event instance).

This method can be used directly as a callback function to trigger chain reactions.

triggered¶: Becomes True if the event has been triggered and its callbacks are about to be invoked.

value¶

The value of the event if it is available.

The value is available when the event has been triggered.

Raises AttributeError if the value is not yet available.

class simpy.events.ConditionValue¶: Result of a Condition. It supports convenient dict-like access to the triggered events and their values. The events are ordered by their occurences in the condition.

class simpy.events.Interrupt¶

Exception thrown into a process if it is interrupted (see interrupt()).

cause provides the reason for the interrupt, if any.

If a process is interrupted concurrently, all interrupts will be thrown into the process in the same order as they occurred.

cause¶: The cause of the interrupt or None if no cause was provided.

simpy.events — Core event types¶

`simpy.events` — Core event types¶