Sets, tuples & sorting
Keep only what is unique
Lesson 9 of 20 · 8 min · Module 3: Working with collections
A set represents unique values. It is useful when duplicates are irrelevant, while a list remains useful when order and repetition matter.
Start this lesson →Free. No installation: you write and run the code in your browser, and it is checked automatically.
By the end, you’ll be able to…
- Choose a collection by its purpose
- Remove duplicates using a set
- Make presentation order explicit
The idea
set(items) removes duplicates. Sets do not promise a useful presentation order. sorted(values) returns a new sorted list.
topics = ["loops", "lists", "loops"]
print(sorted(set(topics))) # ['lists', 'loops']01Compare three collections
A list is an ordered, changeable sequence. A tuple is an ordered sequence that cannot be changed in place. A set keeps unique hashable values and is suited to membership and set operations.
02Separate uniqueness from ordering
Converting to a set answers “which distinct topics exist?” Sorting answers “how should we present them?” Keep those two decisions visible in the code.
Your turn
unique_topics(topics) to return an alphabetically sorted list of unique topic strings. Leave the input unchanged.What the checks look for
- Removes duplicates and sorts
- Handles no topics
- Accepts an immutable tuple
Take this with you
Use the collection that matches the question you are asking.