I would never use a light bulb to heat a ball python. First of all they Hate light! They live in dark burrows under ground and can be very stressed by bright light. The second thing is they suck all the humidity out of the air so keeping that controlled is almost impossible. I would use two under tank heaters one set to 82 and to 92 on thermostats. This will end up costing alot less than a trip to the vet with a sick snake.

I would also recommend an oil filled heater to heat up the room the snakes are in. I keep one in my snake room on a thermostat.

Light bulbs are pet store crap advice so they can sell you more stuff. No Ball python breeder puts light bulbs on there snake, maybe just for pictures.