split by group
import hou
selected = hou.selectedNodes()[0]
groups = [g.name() for g in selected.geometry().primGroups()]
for i, name in enumerate(groups, 1):
#make a split node
split = selected.createOutputNode("blast")
split.setName(name)
split.parm("group").set(name)
split.parm("negate").set(1)
split.moveToGoodPosition()
for node in selected:
out = node.createOutputNode("null")
out.setName("OUT_"+node)
out.moveToGoodPosition()