Dictionaries

A dictionary stores data as key-value pairs. Instead of position numbers, you look things up by a meaningful key, like a name or an id. Dictionaries are everywhere: user profiles, settings, counts, and JSON data all use this shape.

What You'll Learn

• Creating dictionaries and reading values
• Adding, updating, and removing keys
• Looping over keys and values
• Safe lookups with get()

Creating and Reading

Adding and Updating

Assigning to a key that does not exist adds it; assigning to an existing key updates it:

Safe Lookups with get()

Reading a missing key with [ ] raises an error. get() returns None (or a default you choose) instead:

Looping Over a Dictionary

.items() gives you each key and value together:

Nested Dictionaries

A value can itself be a dictionary, which lets you model richer records, like a contact book:

Key Takeaways

• Dictionaries use {key: value} and look up by key
• Assign to add or update; del to remove
• get() avoids errors on missing keys
• .items() loops over keys and values together
• Values can be dictionaries, for nested records