Yeah, I can see the same idea popped up in the comment section. I think its better to call for multiple output ports and not a rejected port, cause then you have more room to create whatever kind of port you need.
try:
something = [x for i,x in enumerate(r) if i % 3 == 0]#just to put something inside the try block
except:
self.pyoutput('<rejected>',Somefeatureyougetthepoint)