06c-substitutions.launch.py

from launch import LaunchDescription
from launch.actions import DeclareLaunchArgument
from launch.substitutions import PathJoinSubstitution
from launch_ros.actions import Node
from launch_ros.parameter_descriptions import ParameterFile
from launch_ros.substitutions import FindPackageShare


def generate_launch_description():
    file_parameters = ParameterFile(
        param_file=PathJoinSubstitution(FindPackageShare('donatello'), 'config', 'sub_params.yaml'),
        allow_substs=True
    )

    return LaunchDescription([
        DeclareLaunchArgument('radius', default_value='1.5'),
        DeclareLaunchArgument('pizza_type', default_value='mushrooms'),
        Node(name='does_machines',
             package='donatello',
             executable='donatello_node',
             parameters=[file_parameters]),
    ])