Warmup

Assign to variable position a tuple of coordinates (1, 5) and then unpack it into variables x and y.

Admin

• Due today: Assignment 3.4, PE 1 Module 3 Quiz
• Do today: Assignment 3.5
• Tomorrow, Friday 9/12:
  • PE 1 Module 3 Test
  • Unit 3 Quiz on paper: lists, tuples and dictionaries

Lesson 3.5 – Dictionaries: Basics

What we’ll learn today

• What a dictionary is
• How to create dictionaries
• Accessing values with keys
• Adding and removing items

Quick Review

• What is the main difference between a tuple and a list?
• Can you change values inside a tuple?

Dictionary Basics

• A dictionary stores key–value pairs.

student = {
    "name": "Alice",
    "age": 16,
    "grade": "10th"
}

Accessing Values

• Use the key inside square brackets.

print(student["name"])   # Alice

Adding Items

student["gpa"] = 3.8
print(student)

Changing Values

student["age"] = 17
print(student)

Removing Items

del student["grade"]
print(student)

Class Question

• How is a dictionary different from a list?

Membership with Keys

• You can test if a key exists.

if "name" in student:
    print("Yes, we have a name!")

Mini Practice

1. Create a dictionary for a pet with keys type, name, and age.
2. Print just the name.
3. Add a new key color.
4. Print the full dictionary.

Mini Challenge

• Write a program that:
  1. Creates a dictionary for a book: title, author, year
  2. Prints the author
  3. Adds the number of pages
  4. Removes the year