Comparing Lists and keep Difference

I am trying to identify Revit (Project Information) Parameters and find those that are either “empty”, “not updated from the Template deafults” or have passed the above to tests.

I thought after identifying those that do not pass, I could take the list of all parameters and remove all those that have been identified with the previous two test.

The problem I am now facing is that the node “List.SetDifference” only seems to return unique values. Since in one of the list one value is repeated (in this example: “734S”, appears in “Project Number” and “CPA Project”) the list of Values is shortened.

Would anyone have a better solution or a fix?
Please note that the entire script is a bit more complex and I would be especially happy if I could only modify this small area.


Sometimes hep is closer than one thinks. Thanks to my colleague Andrew.

Though we are not 100% sure why ‘list2’ has to be set to ‘@L2’ although the input is only a single list.