Understanding the concept of key-value pairs

Welcome, young learners, to an exciting journey into the world of Python dictionaries! In this course, we will embark on an adventure to understand a fascinating concept called “key-value pairs.” Just like a treasure map guides you to hidden riches, understanding key-value pairs will unlock the secrets of organizing and accessing data in Python.

What are Key-Value Pairs? Imagine you have a magical box where you can store your toys. Each toy has a special name (the key), and inside the box, you keep the toy itself (the value). Similarly, in Python, a dictionary is like this magical box. It stores data in pairs: a key, which is like the toy’s name, and a value, which is the actual toy.

Python Code Examples: Let’s dive into some Python code examples to make this concept clearer:

# Creating a dictionary
toy_box = {'teddy bear': 'soft and cuddly', 'ball': 'bouncy', 'blocks': 'stackable'}

# Accessing values using keys
print(toy_box['ball'])  # Output: bouncy

# Adding a new key-value pair
toy_box['car'] = 'vroom vroom'

# Updating the value of an existing key
toy_box['ball'] = 'round and colorful'

# Removing a key-value pair
del toy_box['blocks']

# Checking if a key exists
if 'ball' in toy_box:
    print("We have a ball!")

# Iterating over keys and values
for toy, description in toy_box.items():
    print(f"A {toy} is {description}")

Practice Questions:

1. Accessing Values: What is the description of the toy with the key ‘teddy bear’ in the toy_box dictionary?
2. Adding a New Pair: Add a new toy ‘doll’ with the description ‘pretty’ to the toy_box dictionary.
3. Updating a Pair: Change the description of the ‘ball’ to ‘super bouncy’ in the toy_box dictionary.
4. Removing a Pair: If we remove the key ‘car’ from the toy_box dictionary, how many key-value pairs will be left?

Solutions:

1. Accessing Values: The description of the toy with the key ‘teddy bear’ is ‘soft and cuddly’.
2. Adding a New Pair:

toy_box['doll'] = 'pretty'

3. Updating a Pair:

toy_box['ball'] = 'super bouncy'

4. Removing a Pair: After removing the key ‘car’, there will be 3 key-value pairs left in the toy_box dictionary.

Congratulations, young wizards of Python! You’ve mastered the enchanting world of key-value pairs in dictionaries. Keep practicing your magic, and soon you’ll be conjuring amazing programs with ease!