Brep/Brep list output issue with python: Empty text parameter

My python script (py# BMU shown in figure below) involves creating (by extruding) and translating (move/rotate) of several Breps. Then I decided to output these Breps with one single list, so I extended the Breps in the original lists into a new list called BMU (as shown in figure) and made BMU an output. Everything worked perfect, but for this unique node only. With another file I attached (, with exactly the same script, the output of BMU became ‘Empty text parameter’, which seems to be the normal case. So the question became one of the famous programmer’s problems: “It worked in the first time. Why?”. I’m not sure if it has anything to do with the GUID, such as the same object can only be referenced once in the project.

Rhino File (v7): Mass_15.3dm (2.0 MB)
Succeed script: (4.4 KB)
Failed script: (5.4 KB)

In your file, the BMU output is renamed from the out output of the GHPython component. This is a special output that will convert to text anything sent to it. In that case, you only get the string representation of your list of Breps, rather than the Breps.

Remove the BMU output, add a new input to your GH Python component, rename it to BMU, and you will be back to the same output as in (8.8 KB)

Thank you very much Pierre, that works! Didn’t notice the out output is a special one before, thank you for telling me that!