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  • - What Is a Dictionary in Python?
  • - Accessing and Updating Dictionary Values
  • - Useful Dictionary Methods
  • - Nested Dictionaries
  • - Dictionaries vs Other Data Structures
  • - Real World Example
  • - Mini Exercise

8. Dictionaries and Data Structures

Level: BeginnerDuration: 30m

What Is a Dictionary in Python?

A dictionary in Python is used to store data in **key-value pairs**. Unlike lists that use numeric indexes, dictionaries use meaningful keys to access values.

python
user = {
  "name": "John",
  "age": 25,
  "country": "Nigeria"
}
print(user)

Dictionaries are perfect when you want to label your data for clarity and easy access.

Accessing and Updating Dictionary Values

python
# Access values by key
print(user["name"])  # John

# Add a new key-value pair
user["email"] = "john@example.com"

# Update a value
user["age"] = 26

# Remove a key
user.pop("country")

Useful Dictionary Methods

python
print(user.keys())     # dict_keys(['name', 'age', 'email'])
print(user.values())   # dict_values(['John', 26, 'john@example.com'])
print(user.items())    # dict_items([('name', 'John'), ('age', 26), ('email', 'john@example.com')])

Nested Dictionaries

Dictionaries can contain other dictionaries—this is called nesting. This allows us to structure complex data easily.

python
students = {
  "student1": {"name": "Aisha", "age": 20},
  "student2": {"name": "Kelvin", "age": 22}
}
print(students["student1"]["name"])  # Aisha

Dictionaries vs Other Data Structures

TypeExampleBest Use
List[10, 20, 30]Ordered collection
Tuple("red", "blue")Fixed data
Set{1, 2, 3}Unique items
Dictionary{"name": "Tom"}Structured data with labels

Real World Example

Imagine you're building a user profile feature for a website. A dictionary is a perfect way to store user information.

python
profile = {
  "username": "techgirl",
  "followers": 1200,
  "is_verified": True,
  "skills": ["Python", "Django", "React"]
}
print(profile)

Mini Exercise

Create a dictionary called `car` with keys: `brand`, `model`, `year`. Update the `year`, add a `color`, and print the final dictionary.

python
# Your code here
car = {}
print(car)