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IncludeLaunchDescription

IncludeLaunchDescription method allows to include one launch description (essentially a sub-launch file) inside another, enabling better organization and scalability of complex robot systems. This is particularly useful when you want to break down a large system into smaller, reusable components.

Demo: Very simple

Parent launch file include_demo.launch.py include the args_log_demo.launch.py as sub launch

  • args_log_demo.launch.py use as sub launch
  • include_demo.launch.py us as parent launch
args_log_demo.launch.py
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from launch import LaunchDescription
from launch.actions import DeclareLaunchArgument
from launch.substitutions import LaunchConfiguration
from launch.actions import LogInfo

def generate_launch_description():
    ld = LaunchDescription()

    arg1_decalre = DeclareLaunchArgument('arg1', description="simple arg1 for demo", default_value='hello world')
    arg1 = LaunchConfiguration('arg1')

    log1 = LogInfo(msg=["Argument 'arg1' value: ",arg1])

    ld.add_action(arg1_decalre)
    ld.add_action(log1)
    return ld
include_demo.launch.py
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from launch import LaunchDescription
from launch.actions import IncludeLaunchDescription
from launch.launch_description_sources import PythonLaunchDescriptionSource
from ament_index_python.packages import get_package_share_directory
import os

def generate_launch_description():
    ld = LaunchDescription()
    my_robot_pkg = get_package_share_directory('launch_tutorial')

    robot_launch = IncludeLaunchDescription(
        PythonLaunchDescriptionSource(
            os.path.join(my_robot_pkg, 'launch', 'args_log_demo.launch.py')
        ),
        launch_arguments={
            'arg1': 'call from parent',
        }.items()
    )

    ld.add_action(robot_launch)
    return ld

usage

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ros2 launch launch_tutorial include_demo.launch.py 
# result
[INFO] [launch]: Default logging verbosity is set to INFO
[INFO] [launch.user]: Argument 'arg1' value: call from parent