The Colt Python is a revolver.
NCIS[]
It appeared in the NCIS Season 6 episode, Deliverance (episode).
It reappeared once again in the NCIS Season 11/NCIS: New Orleans backdoor pilot episode, Crescent City (Part 2) (episode) where it is the second sidearm of NCIS Special Agent Dwayne Cassius Pride with the revolver being given the nickname, "Charmaine" and it's also revealed that Pride has been using the revolver for 25 years.
NCIS: Los Angeles[]
It appeared in the NCIS: Los Angeles Season 3 episode, Partners (episode).