How to get argument from launch-file not used in a Node ?

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Hi,

I read a lot of questions about arguments and launch files and did not find something related to my case (maybe this one https://answers.ros.org/question/3755..., but I can't get the value of the LaunchConfiguration)

So here is my pb, I want an argument be used in the launch file to loop on IncludeLaunchDescription instanciation -> I have a yml file working for 1 drone, and i want to use many drones.

def generate_launch_description():
    # ...
    arg_n_drones = DeclareLaunchArgument(
        "N",
        default_value="1",
        description="number of drones in the simulation."
    )  # this does not seem to be enough to have the argument visible with the --show-args option

    N = 1  # I would like something based on arg_n_drones
    l_include_drone_spawn = []
    for i in range(1,N+1):
        l_include_drone_spawn.append(
            IncludeLaunchDescription(
                "launch/spawn_drone.yml",
            )
        )

    return LaunchDescription([
        # ...
        *l_include_drone_spawn,
    ])

Any help appreciated,