does anyone know how to convert a primative group into a polygroup and export? been searching the net without success

I have not tried it in Houdini 17, but in previous versions, the .OBJ export did not support that. There is a script that leverages the Post-Write event field of the export ROP. Place the code in the script field, change the code type to Python and when the export is issued, the code will re-write the resulting .OBJ file to produce a new .OBJ file with material assignments for detected groups. These materials are generally what importers look for.

https://forums.odforce.net/topic/25214-post-processing-an-export/?do=findComment&comment=146948 [forums.odforce.net]

Well it completely failed to work until i realized I was parsing as a hscript, rather than python as you instructed.

So now it works 100%perfectly.

Immense thanks for your help/script!