Dict Update.

Third Data class. You can already create a dictionary and read a value by key. Now the dictionary will change.

Assignment such as profile["weight"] = 75.0 updates an existing key. If the key does not exist, the same syntax adds it: profile["active"] = True.

The items() method yields key-value pairs. You can walk them:

for key, value in profile.items():
    print(key, value)

This lets the code work when a dictionary gains fields. Fields retain insertion order, but most logic should not depend on that order.

Mini example:

book = {"title": "Dune", "copies": 2} book["copies"] = 3 book["available"] = True for key, value in book.items(): print(key, value)

Common mistakes: building a completely new dictionary instead of updating a key, or forgetting the parentheses on items().