clingwrap

Launch? ... Lunch? ... Who knows.

A ROS2 lunch_launch wrapper to simplify writing python launch files.

Usage

Import clingwrap as cw and use LaunchBuilder to generate a launch description in a descriptive way.

from launch import substitutions as sub

import clingwrap as cw


def generate_launch_description():
    l = cw.LaunchBuilder()

    robot_description_path = l.declare_arg("robot_description_path")
    robot_description_urdf = sub.Command(["xacro ", robot_description_path])

    l.node("robot_state_publisher", parameters={"robot_description": cw.as_str_param(robot_description_urdf)})

    return l

See launch_builder.py and launch_helpers.py for the full API. A non-exhaustive list of use cases is presented below.

Nodes

def generate_launch_description():
    l = cw.LaunchBuilder()

    l.node("robot_state_publisher", parameters={"robot_description": "..."})

    return l

Namespace

def generate_launch_description():
    l = cw.LaunchBuilder()

    with l.namespace("my_namespace"):
        l.node("joint_state_publisher_gui")

    return l

Launch Arguments

def generate_launch_description():
    l = cw.LaunchBuilder()

    my_argument = l.declare_arg("my_argument", default_value="hello")
    my_bool_argument = l.declare_bool_arg("my_bool_argument")

    # use my_argument and my_bool_argument as value substitutions
    ...

    return l

use_sim_time Launch Argument

clingwrap automatically adds use_sim_time as a launch argument to all launch descriptions and passes the value into any nodes added to the launch description. The value of the parameter (as a substitution) can be accessed via l.use_sim_time.

Including Other Launch Files

def generate_launch_description():
    l = cw.LaunchBuilder()

    l.include_launch_py("some_package", "my_launch_file.launch.py")

    return l

Composable Nodes

def generate_launch_description():
    l = cw.LaunchBuilder()

    with l.composable_node_container("my_container"):
        l.composable_node(
            "some_package",
            "some_package::ComposableNode",
        )

        l.composable_node(
            "some_other_package",
            "some_other_package::ComposableNode2",
        )

    return l

Remapping Actions

There is an open github issue for this (ros2/ros2#1312). In the meantime:

def generate_launch_description():
    l = cw.LaunchBuilder()

    l.node(
        "some_package",
        "some_executable",
        remappings={
            "a_different_remap": "remap_to_this",
            **cw.remap_action("some_action", "different_action"),
        },
    )

Log Info

def generate_launch_description():
    l = cw.LaunchBuilder()

    l.log("hello world!")

    return l