rclpy.parameter_event_handler module

class rclpy.parameter_event_handler.ParameterCallbackHandle(parameter_name: str, node_name: str, callback: Callable[[rcl_interfaces.msg.Parameter], None])

Bases: object

class rclpy.parameter_event_handler.ParameterEventCallbackHandle(callback: Callable[[rcl_interfaces.msg.ParameterEvent], None])

Bases: object

class rclpy.parameter_event_handler.ParameterEventHandler(node: Node, qos_profile: rclpy.qos.QoSProfile = rclpy.qos.qos_profile_parameter_events, callback_group: CallbackGroup | None = None, event_callbacks: SubscriptionEventCallbacks | None = None, qos_overriding_options: QoSOverridingOptions | None = None, raw: bool = False)

Bases: object

Create ParameterEventHandler.

Usage example:

A class used to “handle” (monitor and respond to) changes to parameters. :param node: Used to subscribe to parameter_events topic :param qos_profile: A QoSProfile or a history depth to apply to the subscription.

In the case that a history depth is provided, the QoS history is set to KEEP_LAST, the QoS history depth is set to the value of the parameter, and all other QoS settings are set to their default values.

Parameters:

  • callback_group – The callback group for the subscription. If None, then the default callback group for the node is used.

  • event_callbacks – User-defined callbacks for middleware events.

  • qos_overriding_options – Options to customize QoS parameter overrides.

  • raw – If True, then received messages will be stored in raw binary representation.

class Callbacks

Bases: object

Create a Callbacks container for ParameterEventHandler.

Callbacks container is used to store and manage parameter and parameter-event callbacks

add_parameter_callback(parameter_name: str, node_name: str, callback: Callable[[rcl_interfaces.msg.Parameter], None]) → ParameterCallbackHandle

Add new parameter callback.

Callbacks are called in FILO manner.

Parameters:

  • parameter_name – Name of a parameter to bind the callback to

  • node_name – Name of a node, that the parameter should be related to

  • callback – A callable to be called when a parameter event occurs

Return ParameterCallbackHandle:

A handle that should be saved by the user so that the callback can be later removed.

add_parameter_event_callback(callback: Callable[[rcl_interfaces.msg.ParameterEvent], None]) → ParameterEventCallbackHandle

Add new parameter event callback.

Callbacks are called in FILO manner.

Parameters:

callback – A callable to be referenced on a ParameterEvent

Return ParameterEventCallbackHandle:

A handle that should be saved by the user so that the event_callback can be later removed.

event_callback(event: rcl_interfaces.msg.ParameterEvent) → None

Search for callback and execute it.

Method to be utilized by ParameterEventHandler object as a callback for subscription to a /parameter_events topic. Used to traverse parameter_callbacks dict and perform callbacks, related to Parameter, specified in event.

Parameters:

event – ParameterEvent message. By design, originates from /parameter_events topic

remove_parameter_callback(handle: ParameterCallbackHandle) → None

Remove the parameter callback related to provided handle.

Parameters:

handle – The handle of the callback that is to be removed

remove_parameter_event_callback(handle: ParameterEventCallbackHandle) → None

Remove the parameter event callback related to provided handle.

Parameters:

handle – A handle of the callback that is to be removed

add_parameter_callback(parameter_name: str, node_name: str, callback: Callable[[rcl_interfaces.msg.Parameter], None]) → ParameterCallbackHandle

Add new parameter callback.

Callbacks are called in FILO manner.

The configure_nodes_filter() function will affect the behavior of this function. If the node specified in this function isn’t included in the nodes specified in configure_nodes_filter(), the callback will never be called.

Parameters:

  • parameter_name – Name of a parameter to tie callback to

  • node_name – Name of a node, that the parameter should be related to

  • callback – A callable to be called when the parameter is modified

Return ParameterCallbackHandle:

A handle that should be saved by the user so that the event_callback can be later removed.

add_parameter_event_callback(callback: Callable[[rcl_interfaces.msg.ParameterEvent], None]) → ParameterEventCallbackHandle

Add new parameter callback.

Callbacks are called in FILO manner.

Parameters:

callback – A callable to be referenced on a ParameterEvent

Return ParameterEventCallbackHandle:

A handle that should be saved by the user so that the event_callback can be later removed.

configure_nodes_filter(node_names: List[str] | None = None) → bool

Configure which node parameter events will be received.

This function depends on rmw implementation support for content filtering. If middleware doesn’t support contentfilter, return false.

If node_names is empty, the configured node filter will be cleared.

If this function return true, only parameter events from the specified node will be received. It affects the behavior of the following two functions. - add_parameter_event_callback()

The callback will only be called for parameter events from the specified nodes which are configured in this function.

  • add_parameter_callback() The callback will only be called for parameter events from the specified nodes which are configured in this function and add_parameter_callback(). If the nodes specified in this function is different from the nodes specified in add_parameter_callback(), the callback will never be called.

Parameters:

node_names – Node names to filter parameter events from

Returns:

True if the filter was successfully applied, False otherwise.

Raises:

RCLError if internal error occurred when calling the rcl function.

destroy() → None
static get_parameter_from_event(event: rcl_interfaces.msg.ParameterEvent, parameter_name: str, node_name: str) → rcl_interfaces.msg.Parameter | None

Get specified parameter value from ParameterEvent message.

Parameters:

  • event – ParameterEvent message to be read

  • parameter_name – Name of a parameter to get from ParameterEvent message

  • node_name – Name of a node, that the parameter should be related to

Return Optional[Parameter]:

If specified parameter is found, returns Parameter object. Otherwise, returns None

static get_parameters_from_event(event: rcl_interfaces.msg.ParameterEvent) → Iterable[rcl_interfaces.msg.Parameter]

Get all parameters from a ParameterEvent message.

Parameters:

event – ParameterEvent message to read

remove_parameter_callback(handle: ParameterCallbackHandle) → None

Remove a ParameterCallbackHandle.

Perform no callbacks on this parameter events in the future.

Parameters:

handle – ParameterCallbackHandle of a callback to be removed

remove_parameter_event_callback(handle: ParameterEventCallbackHandle) → None

Remove a ParameterEventCallbackHandle.

Perform no callbacks on parameter events in the future.

Parameters:

handle – ParameterEventCallbackHandle of a callback to be removed