I didn't go into as much detail as I would have liked about hot reloaders, but the tl;dr is that if you have a _single_ reference to something, then hot reloading it is somewhat simple. The problem comes when you want to hot reload a single module inside a large program.

Hot reloading a loop like this is super cool, but it only works if you're just changing constants and not defining anything. The moment you want to change the definitions of an object in the loop and hot reload it then you're in a lot of pain.

Here's the source code for IPythons autoreload magic command: https://github.com/ipython/ipython/blob/cd54f15544eee69449cc.... Take note of the Caveats section.