Dictionaries as Key-Value Maps
Explore Python dictionaries as a fundamental data structure that uses unique keys to map values, enabling clear and efficient data representation. Understand dictionary creation, value lookup, insertion and updating, key existence checks, and iteration techniques for managing complex information.
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As studied earlier, lists are excellent for ordered sequences, but they have a major limitation: we must know the exact position (index) of an item to retrieve it. If we want to store a user’s profile, remembering that their email is at index 2 and their username is at index 0 is error-prone and hard to read. We need a data structure that lets us label our data.
In Python, we use dictionaries to map unique labels (also called keys) to specific values, allowing us to look up information by name. This structure makes it easy to represent a single object with multiple named attributes, such as a product in an inventory, where each attribute (e.g., name, price, quantity) is accessed directly through its corresponding key.
Defining a dictionary
A dictionary is a collection of key-value pairs. We define a dictionary using curly braces {}, separating keys and values with a colon :.
Unlike lists, dictionaries are unordered in terms of access (though Python 3.7+ preserves insertion order for display). We do not access items by position; we access them by their key.
Keys must be unique and immutable (usually strings or numbers).
Values can be any type: strings, integers, lists, or even other ...