Dictionaries vs Lists — Choosing the Right Tool

"You now know both lists and dictionaries well. But knowing when to use which is a skill in itself. Should your expenses be a list or a dictionary? Should categories be a list or a dictionary? The wrong choice leads to awkward, inefficient code. The right choice makes everything feel natural. Today you develop the instinct for choosing the right data structure — and more importantly, you learn how to combine them into the powerful list-of-dicts pattern that powers almost every real application."