In high school biology (IIRC), our teacher told us about two incidents involving large pythons attacking their owners, with one being a fatality and the other nearly so. Both snakes had formerly been docile, and both incidents involved feeding the snakes; as I recall, they hadn't cleaned up well enough after preparing the food, or something like that, and the snakes struck on scent. This would've been in the early '80s when he told us.They are capable of killing humans. I'm not aware of any yet, but I could be wrong.