LOPs - primvars creation

from pxr import Usd, UsdGeom, Sdf

# Get the current USD stage
stage = hou.pwd().editableStage()

# Loop through all primitives in the USD stage
for prim in stage.Traverse():
    # Check if this primitive is an Xform and has '/Prototypes' in its path (prototype)
    if prim.IsA(UsdGeom.Xform) and "/Prototypes" in prim.GetPath().pathString:
        proto_path = prim.GetPath().pathString  # Get the prototype path

        # Extract the last part of the path to use as the envTreesID value
        proto_index = proto_path.split("/")[-1]  # This is the value you want to assign
        mesh_index = proto_path.split("/")[-4]  # This is the value you want to assign

        # Create and set the primvar as a string
        attr = prim.CreateAttribute("primvars:dneg:envTreesID", Sdf.ValueTypeNames.String)
        attr.Set(proto_index)
        
        # Loop through the children of this Xform (prototype) to find meshes
        for child_prim in prim.GetChildren():
            # Check if the child primitive is a mesh (UsdGeom.Mesh)
            if child_prim.IsA(UsdGeom.Mesh):
                # Create and set the primvar on the mesh with the correct envTreesID value
                mesh_attr = child_prim.CreateAttribute("primvars:dneg:envTreesID", Sdf.ValueTypeNames.String)
                mesh_attr.Set(mesh_index)  # Set the correct envTreesID value

print("Assigned the correct envTreesID value to meshes within prototypes.")