The Python was the original guardian deity of Delphi. Living on Mt. Parnassus, no one dared to approach. The people prayed for help, and Apollo answered their call. With one arrow from his bow, Apollo killed the serpent. Because of this, the Oracle at Delphi was dedicated to Apollo.
Plutarch. The Fall of the Roman Republic.
Oxford Concise Companion to Classical Literature. ed. Howatson and Chilvers. Oxford. New York, 1993.