A bird house is a bad idea for a few different reasons...

1. The wood would be hard to clean, no matter how you sealed it.

2. You wouldn't be able to get the snake out of it when you needed to.

3. Your ball python will continue to grow and eventually become bigger than the typical circular opening of a bird house and could become stuck.

The very best hides are those that are easily cleaned, and that you can simply lift off with as little disturbance of the animal as possible. The RBI hides shown in the post above this one are excellent, but you can use any number of things, from store bought to homemade.