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

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 flag 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).

value

The value of the event if it is available.

The value is available when the event has been triggered.

Raise a 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.

Raise a 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.

Raise a ValueError if exception is not an Exception.

Raise a 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.

fail(exception)

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

Raise a ValueError if exception is not an Exception.

Raise a RuntimeError if this event has already been 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.

Raise a 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.

Raise a 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.

fail(exception)

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

Raise a ValueError if exception is not an Exception.

Raise a RuntimeError if this event has already been 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.

Raise a 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.

Raise a 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.

fail(exception)

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

Raise a ValueError if exception is not an Exception.

Raise a RuntimeError if this event has already been 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.

Raise a 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.

Raise a 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.

fail(exception)

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

Raise a ValueError if exception is not an Exception.

Raise a RuntimeError if this event has already been 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.

Raise a 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.

Raise a 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.

fail(exception)

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

Raise a ValueError if exception is not an Exception.

Raise a RuntimeError if this event has already been 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.

Raise a 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.

Raise a 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.

fail(exception)

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

Raise a ValueError if exception is not an Exception.

Raise a RuntimeError if this event has already been 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.

Raise a 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.

Raise a 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.

fail(exception)

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

Raise a ValueError if exception is not an Exception.

Raise a RuntimeError if this event has already been 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.

Raise a 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.

Raise a 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.

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