Hello Future Coders!

Welcome to Week 14 of our Python Adventures! This week, we're exploring dictionaries—those super smart containers that let you find things by name instead of numbers. Think of them as your personal phone book where you look up someone's name to find their number. Ready to become a dictionary master? Let's go!

Objective

Learn what a dictionary is and how it's different from lists.
Discover how to create dictionaries with keys and values.
Master adding, changing, and finding information using keys.
Practice using dictionaries with simple, fun examples.
Solidify your understanding with fill‑in‑the‑blank exercises and debugging challenges.

1. What Is a Dictionary?

Explanation

A dictionary is like a special container where every item has a name tag (called a key) and the actual item (called a value). Instead of using numbers like lists, you use names to find what you want!

Analogy

Imagine your phone book:

You look up a name (the key) like "Mom".
You find the phone number (the value) like "555-1234".
You don't need to remember position numbers.
You can add new contacts easily.
You can change numbers when people move.

That's exactly how Python dictionaries work—they're your digital phone book!

2. Creating Your First Dictionary

Syntax

dictionary_name = {"key1": "value1", "key2": "value2"}

Curly braces {} create the dictionary.
Colons : connect keys to values.
Commas , separate each pair.

Example: My Family's Phone Numbers

phone_book = {"Mom": "555-1234", "Dad": "555-5678", "Sister": "555-9999"}
print("My phone book:", phone_book)

# Finding someone's number
print("Mom's number:", phone_book["Mom"])
print("Dad's number:", phone_book["Dad"])

What happens?

Python creates a dictionary with 3 contacts, and you can find anyone's number by typing their name!

3. Interactive Fill‑in‑the‑Blanks

Pet Information

Complete the blanks to create a dictionary about pets:

 my_pet = {"name": "Fluffy", "type": ______, "age": ______}  # Add "cat" and 3
 print("My pet info:", my_pet)

 # Get pet's name
 pet_name = my_pet[______]  # What key gets the name?
 print("My pet's name is", pet_name)

(Hint: Use the key names exactly as written!)

Favorite Things

 favorites = {"color": "blue", "food": "pizza"}

 # Add a new favorite
 favorites[______] = "soccer"  # What key for favorite sport?

 print("My favorites:", favorites)

(Hint: Think of a good key name for sports!)

4. Adding and Changing Information

Adding New Items

student_grades = {"Math": 85, "Science": 92}
print("Original grades:", student_grades)

# Adding a new subject
student_grades["English"] = 88
print("After adding English:", student_grades)

# Adding more subjects
student_grades["Art"] = 95
print("All grades:", student_grades)

Changing Existing Items

game_scores = {"Level1": 100, "Level2": 150, "Level3": 200}
print("Original scores:", game_scores)

# Beat your high score!
game_scores["Level2"] = 180  # New high score!
print("Updated scores:", game_scores)

5. Checking What's Inside

backpack_items = {"pencils": 5, "erasers": 2, "rulers": 1}

# Check if we have something
if "pencils" in backpack_items:
    print("Great! I have", backpack_items["pencils"], "pencils")

# Safe way to check
pencil_count = backpack_items.get("pencils", 0)  # Returns 0 if not found
print("Pencil count:", pencil_count)

# Get all keys (names) and values (amounts)
print("All items:", list(backpack_items.keys()))
print("All amounts:", list(backpack_items.values()))

6. Debugging Challenge

Fix the errors in this code so it runs without mistakes:

# Create a dictionary of favorite movies
movies = ["Action": "Avengers", "Comedy": "Toy Story"]  # What's wrong here?
print("My movies:", movies)

# Add a new movie
movies{"Horror"} = "Monster Movie"  # How do we add to dictionaries?

# Check a movie
if "Action" in movies:
    print("I love action movies!")

(Hint: Check the dictionary creation and how to add new items.)

7. Hands‑On Mini‑Projects

A. Student Report Card

# Create a simple report card
report_card = {"Math": 90, "English": 85, "Science": 88}

# Add a new subject
report_card["History"] = 92

# Show all grades
for subject in report_card:
    grade = report_card[subject]
    print(f"{subject}: {grade}")

B. Pet Profile

# Create your pet's profile
pet_profile = {"name": "Buddy", "animal": "dog", "age": 3}

# Update age (birthday!)
pet_profile["age"] = 4

# Add new info
pet_profile["color"] = "brown"

print("Pet Profile:")
for key in pet_profile:
    print(f"{key}: {pet_profile[key]}")

C. Simple Store

store_prices = {"apple": 1, "banana": 2, "orange": 3}

# Customer wants to buy something
item = "apple"
if item in store_prices:
    price = store_prices[item]
    print(f"{item} costs ${price}")
else:
    print("Sorry, we don't have that!")

8. Interactive Challenge: Magic Contact Book

Fill in the blanks to create a simple contact manager:

contacts = {}  # Start empty

# Add first contact
name = "Alice"
phone = "555-1111"
contacts[____] = ____  # (a) How do we add name and phone?

# Add second contact
contacts["Bob"] = "555-2222"

# Look up someone
search_name = "Alice"
if search_name ___ contacts:  # (b) How do we check if key exists?
    phone_number = contacts[search_name]
    print(f"{search_name}'s number is {phone_number}")

# Show all contacts
print("All contacts:")
for name ___ contacts:  # (c) How do we loop through keys?
    print(f"{name}: {contacts[name]}")

(Hints: (a) name, phone, (b) in, (c) in)

9. Simple Dictionary Functions

def add_score(score_dict, player, points):
    score_dict[player] = points
    print(f"Added {player} with {points} points!")

def get_score(score_dict, player):
    if player in score_dict:
        return score_dict[player]
    else:
        return 0

# Test it:
game_scores = {}
add_score(game_scores, "Player1", 100)
add_score(game_scores, "Player2", 85)

print("Player1 score:", get_score(game_scores, "Player1"))
print("Player3 score:", get_score(game_scores, "Player3"))

Recap & Reflection

Dictionaries store pairs of keys and values, like a phone book.
Curly braces {} create dictionaries, colons : connect pairs.
Keys are the names you use to find values (like contact names).
Values are the information you store (like phone numbers).
Square brackets [] access values: my_dict["key"].

Discussion Prompt:

If you could create a magical dictionary that knew everything about your favorite video game, what keys would you use and what information would you store?

Next Week Preview:

Get ready to become debugging detectives! We'll learn how to find and fix errors in our code like real programmers. Every coder makes mistakes—the good ones know how to fix them!

Week 14 - Dictionaries: Your Personal Phone Book