Dicts: Key-Value Storage

Dictionaries are one of Python's most powerful and frequently used data structures. They store key-value pairs, allowing you to look up values by their keys instantly. Think of a dictionary like a real dictionary: you look up a word (key) to find its definition (value). The difference is that Python dictionaries can use almost any immutable type as a key, not just strings. In data engineering, dictionaries are absolutely everywhere. JSON responses from APIs are dictionaries. Configuration files parse into dictionaries. Database rows are often represented as dictionaries. Caches use dictionaries. Environment variables are accessed through dictionaries. Mastering dictionaries is essential for any Python developer. Notice how the dictionary uses descriptive string keys like "user_id" and "nam