How would you heat this type of enclosure?

[stkkts]

I have a all wood dresser i was thinking of converting into a tank for my ball python. It shouldnt be that hard. the one question i had though, was how would you heat it? I could put holes in the outside, and screen over the hole, so the heat could get in, but thats kind of a fire hazard. I have seen some people put the lights inside the tank, but i dont understand how they do that, and not have the animal burn itself. Please help me figure out a way to heat this design. thanks in advance.