Here's the gist of how Python deals with garbage collection, in simple terms. Think of any object you create (a list, a dictionary, etc.) as a balloon. Every variable that points to it is a string holding it down. Python's main job is just counting the strings. When you get rid of the last variable pointing to an object—by reassigning it or because it goes out of scope—the "reference count" drops to zero. At that point, Python knows the balloon has no strings left and it can be cleared from memory. That's it for 99% of cases. It also has a separate, smarter collector that runs every so often to clean up weird edge cases (like two objects that only point to each other), but you almost never have to think about it. It’s one of those features that just works.