http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&t=22021&highlight=&sid=b3d35d7dbeb7e1e8c729ed199ccf1723
http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&p=102109&sid=79ca6a0899568ba575f4f09b0ced4282
http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&p=122000&sid=84a64815ec345d3ec0a44aac2bdda8dd
Basic Code to get selected prim string
import toolutils
viewer = toolutils.sceneViewer()
geo = viewer.selectGeometry()
prims = geo.mergedSelectionString()
If you want get list of Prims
listPrim = hou.selectedNodes()[0].geometry().globPrims(prims)
Just list of Prim numbers
listPrimNum = []
for i in listPrim:
listPrimNum.append(i.number())