Dictionaries

A dictionary for your ideas

Lesson 7 of 20 · 7 min · Module 3: Working with collections

A dictionary connects a meaningful key to a value. It is useful when a list alone does not tell the whole story.

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By the end, you’ll be able to…

Create a dictionary with meaningful keys
Read an optional value using get
Choose a suitable default

The idea

Create a dictionary with curly braces. Read a value using square brackets, such as profile["name"]. Use .get(key, default) when a key might be missing.

profile = {"name": "Alex", "lessons": 5}
print(profile["name"])

01Keys and values play different roles

In {"name": "Alex", "lessons": 5}, the keys describe what the values mean. Dictionary keys are looked up exactly, so spelling and capitalization matter.

02A default handles missing information

person.get("lessons", 0) returns the stored count when it exists and zero when it does not. It does not add a new key to person.

person = {"name": "Sam"}
print(person.get("lessons", 0))

Output

Your turn

Create profile with the keys "name": "Alex" and "lessons": 5. Define remaining(person) to return how many of 10 lessons remain, using zero when the lessons key is missing.

What the checks look for

Dictionary stores a name and lesson count
Five lessons remain for Alex
Handles a missing lessons key
Works with a different lesson count

Try it in the editor →

Take this with you

A dictionary connects meaning to data; a default makes an expected absence explicit.