PyPyPath

Module 5: Lists in Python

Modifying Lists

You can change list items directly by index, or update a slice with new values. This is what “mutable” means in practice.

About 10 minutes

Change one item

Example code
grades = [70, 80, 90]
grades[1] = 85   # change 80 to 85
print(grades)

Change a slice

Example code
nums = [1, 2, 3, 4, 5]
nums[1:3] = [20, 30]
print(nums)  # [1, 20, 30, 4, 5]

Extend with another list

Example code
a = [1, 2]
b = [3, 4]
a.extend(b)
print(a)  # [1, 2, 3, 4]
Practice

Create prices = [10, 20, 30]. Change middle price to 25. Add 40 at the end. Print.

Key takeaways

  • list[i] = new_value changes one item.
  • Slice assignment replaces multiple items at once.
  • extend() adds all items from another list.

Quick check: Modifying Lists

Question 1 of 2

To change the second item in lst, you write: