How can I call a ros2 executable with arguments from a non-ROS file

edit

Hello,

I have two questions: I would like to create a ROS API to start ROS nodes from a non-ROS python script. For example the non-ROS python script: pick.py, would call the pick_ros.py to start a node (assuming that ROS is already running). Even though this is not elegant, the only way I found to do that, is by writing in the Python script the terminal command: os.system("ros2 run package pick") My first question, is there another way to run ros2 run within Python?

Second, the pick method of the pick_ros executable ideally should take three arguments: x, y, z. Is there a way to call the ros node with arguments, without declaring these as ros parameters? (the reason is, that the pick_ros.py calls smach (state machine), which is not a node. And declaring parameters can be done only in nodes) So I would like something like: ros2 run package pick x=0.2, y=0.2, z=0.2

Edit: Declaring parameters however raises a type error:

I get x, y, z values from an action message (as floats - double type is not valid), whether ROS parameter types only accepts double type (no float) which for a reason identifies it as a type error.

In particular, my action msg is:

# Request
float64 x
float64 y
float64 z

and the pick node is:

def pick_sm(x=0.2, y=0.3, z=0.2):
    rclpy.init(args=None)

    node = rclpy.create_node('pick')

    node.declare_parameter('x')
    node.declare_parameter('y')
    node.declare_parameter('z')

    x_par = Parameter('x', Parameter.Type.DOUBLE, x)
    y_par = Parameter('y', Parameter.Type.DOUBLE, y)
    z_par = Parameter('z', Parameter.Type.DOUBLE, z)

When I call the pick_sm node through a non-ROS python script, I get this error:

AssertionError: The 'x' field must be of type 'float'

which prevents me from using these x, y, z fields as ROS parameters

Thank you in advance