Set a single value of an user parameter array from Python API

MattiaDeiRossi

Hi all,

I set up this user parameter in the mcx project

{
  "Version": "1.0",
  "Children": [
    {
      "Name": "IO",
      "Children": [
        {
          "Name": "Outputs",
          "Type": "bool[16],parameter_volatile"
        },
        {
          "Name": "Inputs",
          "Type": "bool[24],input"
        }
      ]
    },

From the desk I can set a single value each time ponting the path root/UserParameters/IO/Outputs/ch7 and also from the GRID it works but from the Python API the same path doesn't work, is this the right behavior?

values = [False]*16
values[7] = True
req.setParameter("root/UserParameters/IO/Outputs", values).get() ##working
 
req.setParameter("root/UserParameters/IO/Outputs/ch7",True).get() ## not working

Philippe

Hi Mattia,

In the Python API you need to use offset and length to set single elements in an array. You cannot use the /chX path attribute, this does not actually exist in the tree and is only used to visualize in DESK and GRID.

See below for the documentation of the SetParameter function:

def setParameter(self, path, value, type_name=None, offset=0, length=0):
    """Set a new value to a parameter with a given path

        Args:
            path(str): parameter path in the tree
            value(any): new parameter value
            type_name(str): type of the value (by default, resolved automatically)
            offset(int): offset of the elements to update in the destination array, (by default, is 0)
            length(int): number of the elements to update in the destination array, (by default, takes length of the
            value argument)

        Returns:
              Reply(StatusMsg): A Promise, which resolves when a parameter value is updated or fails otherwise.

        Examples:
              >>> reply = req.setParameter("root/Control/activateSemiAuto", False)
              >>> reply.get()
              >>> reply = req.setParameter("root/Control/targetJointAngles", [0.2, 3.14, 0.4])
              >>> reply.get()
    """