Python · Beginner level

Beginner level · Module 3: Working with Lists, Dictionaries and Strings · Lesson 1 of 3

Lists and List Operations

Store ordered collections and use list methods to add, remove, sort and search items.

In this lesson you will

  • Add, remove and sort list items
  • Use indexing, slicing and the in operator

Key concepts

indexappend/remove/sortslicingmembership test

The lesson

A list holds several values in order: items = ["rice", "sugar", "soap"]. Each item has an index starting at 0, so items[0] is the first item and items[-1] the last.

Lists can change. append() adds to the end, remove() deletes the first matching value, insert() adds at a position, and sort() puts the items in order. len(items) tells you how many there are, and the in operator checks membership: "soap" in items.

Slicing takes part of a list: items[:3] gives the first three items. Slices never cause an index error, even if the list is shorter than you expect.

Step by step

  1. Create an empty shopping list.
  2. Add three items read from input() with append().
  3. Remove an item after checking it is in the list.
  4. Sort the list and print the first three items with a slice.

Practice activity

Manage a shopping list: add items from input, remove a bought item, sort the list and print the first three items.

Expected result: A correctly updated, sorted list printed with the first three items.

Check your understanding

  1. What does items[-1] return?

    Show answer

    The last item in the list.

  2. What is the difference between list.sort() and sorted(list)?

    Show answer

    sort() changes the original list; sorted() returns a new sorted list and leaves the original unchanged.

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