partial class Examples
{
  public static Rhino.Commands.Result DetermineObjectLayer(Rhino.RhinoDoc doc)
  {
    Rhino.DocObjects.ObjRef obref;
    Rhino.Commands.Result rc = Rhino.Input.RhinoGet.GetOneObject("Select object", true, Rhino.DocObjects.ObjectType.AnyObject, out obref);
    if (rc != Rhino.Commands.Result.Success)
      return rc;
    Rhino.DocObjects.RhinoObject rhobj = obref.Object();
    if (rhobj == null)
      return Rhino.Commands.Result.Failure;
    int index = rhobj.Attributes.LayerIndex;
    string name = doc.Layers[index].Name;
    Rhino.RhinoApp.WriteLine("The selected object's layer is '{0}'", name);
    return Rhino.Commands.Result.Success;
  }
}

import Rhino
import scriptcontext
import System.Guid

def DetermineObjectLayer():
    rc, obref = Rhino.Input.RhinoGet.GetOneObject("Select object", True, Rhino.DocObjects.ObjectType.AnyObject)
    if rc!=Rhino.Commands.Result.Success: return rc
    rhobj = obref.Object()
    if rhobj is None: return Rhino.Commands.Result.Failure
    index = rhobj.Attributes.LayerIndex
    name = scriptcontext.doc.Layers[index].Name
    print("The selected object's layer is '", name, "'")
    return Rhino.Commands.Result.Success

if __name__ == "__main__":
    DetermineObjectLayer()