ROS2 launch nodes by python script

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This can be accomplished using the LaunchService class.

Basic example:

main.py:

from launch import LaunchService

from my_launch_file import generate_launch_description


launch_service = LaunchService()
launch_service.include_launch_description(generate_launch_description())
launch_service.run()

In this case, generate_launch_description() comes from a typical ros2 launch file. For example:

my_launch_file.py:

from launch import LaunchDescription
from launch_ros.actions import Node

def generate_launch_description():
    rviz_node = Node(
        package='rviz2',
        executable='rviz2',
        name='my_rviz_node'
    )
    return LaunchDescription([
        rviz_node,
    ])