Butter has a lot of calories, but very little lactose. The amount of lactose depends on the processing, but clarified butter or ghee will have almost none. The butter making process separates the water from the fat, and the lactose remains with the water component.
Milk, on the other hand, contains a lot of lactose. It is found in human milk, cow's milk, goat's milk, sheep milk, in varying quantities. Oh yes, yak and buffalo too. Milk = lactose.