ros2_pyterfaces 0.1.2

ROS 2 interface definitions, serialization, hashes, and ROS Python conversions

ROS 2 PyTerfaces IDL

ROS 2 message and service definitions, metadata and serialization in Python.

Create new message types, (de)serialize them, compute the RIHS01 hash, and convert to and from ROS 2 Python messages. All ROS 2 common_interfaces are reimplemented, and every message tested to interoperate with ROS.

Based on Cyclone DDS IDL, but specialized for ROS 2.

[!NOTE] This is a low level tool to send/receive raw payload with ROS 2, and to set up communications on the RMW.

Table of Contents

• Install
• Example
  • Message
  • Service
  • Utilities
• Attribution
• Replicated ROS 2 Repos
  • Included Interfaces

Install

pip install ros2_pyterfaces

Example

Message

from dataclasses import dataclass
from ros2_pyterfaces.idl import IdlStruct, types

@dataclass
class Vector3(IdlStruct, typename="geometry_msgs/msg/Vector3"):
    x: types.float64 = 0.0
    y: types.float64 = 0.0
    z: types.float64 = 0.0

my_msg: Vector3 = Vector3(1,2,3)

# serialization
blob_bytes: bytes = my_msg.serialize()
my_msg_again: Vector3 = Vector3.deserialize(blob_bytes)

# ROS 2 metadata
json_type_description = Vector3.json_type_description()
ros_hash = Vector3.hash_rihs01()

# ROS 2 conversion
ros_msg_type = Vector3.to_ros_type()
ros_msg = my_msg.to_ros()
our_msg: Vector3 = Vector3.from_ros(ros_msg)

Service

Services follow the ROS naming pattern: *_Request, *_Response, *_Event, plus a small wrapper type. The serializable types are the request, response, and event dataclasses. The top-level service type is usually created with make_idl_service(...). If you omit event_type=... (most cases), the factory generates a matching event type for you.

from dataclasses import dataclass
from ros2_pyterfaces import idl

# Same classes definition as Messages for *_Request *_Response
@dataclass
class SetBool_Request(idl.IdlStruct, typename="std_srvs/srv/SetBool_Request"):
    data: bool = False


@dataclass
class SetBool_Response(idl.IdlStruct, typename="std_srvs/srv/SetBool_Response"):
    success: bool = False
    message: str = ""

# Top-level service type
SetBool = idl.make_idl_service(SetBool_Request, SetBool_Response)

# Serialization
some_request: SetBool_Request = SetBool.Request(data=True)
some_response: SetBool_Response = SetBool.Response(success=True, message="yey")

# ROS 2 metadata
json_type_description = SetBool.json_type_description()
ros_hash = SetBool.hash_rihs01()

# ROS 2 conversion
ros_srv_type = SetBool.to_ros_type()

ros_request = some_request.to_ros()
request_again = SetBool.Request.from_ros(ros_request)

ros_response = some_response.to_ros()
response_again = SetBool.Response.from_ros(ros_response)

[!WARNING] Not implemented yet:

• Actions

Utilities

You can normalize messages to plain nested Python data for comparisons, tests, and snapshots:

from ros2_pyterfaces import idl

plain = idl.message_to_plain_data(my_msg)
plain_ros = idl.message_to_plain_data(my_msg.to_ros(), type(my_msg))
assert plain == plain_ros

There is also a deterministic random message generator for repeatable tests:

from ros2_pyterfaces.geometry_msgs.msg import Vector3
from ros2_pyterfaces.utils.random import random_message

msg = random_message(Vector3)
same_msg_again = random_message(Vector3)
assert msg == same_msg_again

Attribution

The low-level IDL model, serialization behavior, and part of the user API are dependent on (fantastic) Cyclone DDS Python's idl: https://github.com/eclipse-cyclonedds/cyclonedds-python.

Replicated ROS 2 Messages Repos

• common_interfaces
• rcl_interfaces
• unique_identifier_msgs

Included Interfaces

• ros2_pyterfaces.builtin_interfaces: msg.py
• ros2_pyterfaces.composition_interfaces: srv.py
• ros2_pyterfaces.diagnostic_msgs: msg.py, srv.py
• ros2_pyterfaces.geometry_msgs: msg.py
• ros2_pyterfaces.lifecycle_msgs: msg.py, srv.py
• ros2_pyterfaces.nav_msgs: msg.py, srv.py
• ros2_pyterfaces.rcl_interfaces: msg.py, srv.py
• ros2_pyterfaces.rosgraph_msgs: msg.py
• ros2_pyterfaces.sensor_msgs: msg.py, srv.py
• ros2_pyterfaces.service_msgs: msg.py
• ros2_pyterfaces.shape_msgs: msg.py
• ros2_pyterfaces.statistics_msgs: msg.py
• ros2_pyterfaces.std_msgs: msg.py
• ros2_pyterfaces.std_srvs: srv.py
• ros2_pyterfaces.stereo_msgs: msg.py
• ros2_pyterfaces.test_msgs: msg.py
• ros2_pyterfaces.type_description_interfaces: msg.py, srv.py
• ros2_pyterfaces.trajectory_msgs: msg.py
• ros2_pyterfaces.unique_identifier_msgs: msg.py
• ros2_pyterfaces.visualization_msgs: msg.py, srv.py