Chapter 2: Variables and Data Types¶

🚀 Open Notebook¶

📺 Video Tutorial¶

Learn Python VARIABLES in 10 minutes! ❎ (10:20)

�📚 What You’ll Learn¶

Variables are fundamental in programming - they let you store and manipulate data in your programs!

🎯 Learning Objectives¶

Understand what variables are and how to create them
Learn about Python’s basic data types (str, int, float, bool)
Practice using f-strings to format output
Combine variables with conditional statements

📖 Concept Explanation¶

What are Variables?¶

Variables are named containers that store data values. Think of them as labeled boxes where you can put different types of information.

name = "Alice"  # name is the variable, "Alice" is the value
age = 25        # age stores the number 25

Python’s Basic Data Types¶

1. String (str) - Text Data¶

name: str = "John"
message: str = "Hello, World!"

Strings hold text
Must be enclosed in quotes (single or double)

2. Integer (int) - Whole Numbers¶

age: int = 20
quantity: int = 100

Integers are whole numbers (no decimals)
Can be positive or negative

3. Float (float) - Decimal Numbers¶

price: float = 19.99
pi: float = 3.14159

Floats are numbers with decimal points
Used for precise calculations

4. Boolean (bool) - True or False¶

is_student: bool = True
is_available: bool = False

Booleans can only be True or False
Used for logic and conditions

Type Annotations¶

The : type syntax is called a type hint:

name: str = "Alice"  # Explicitly states this is a string

Type hints are optional but make code more readable!

F-Strings (Formatted Strings)¶

F-strings let you embed variables directly in strings:

name = "Alice"
age = 25
print(f"My name is {name} and I am {age} years old")
# Output: My name is Alice and I am 25 years old

💡 Examples¶

Creating Variables¶

# String variable
favorite_food: str = "Pizza"

# Integer variable
student_count: int = 30

# Float variable
temperature: float = 72.5

# Boolean variable
is_raining: bool = False

Using Variables¶

first_name = "John"
last_name = "Doe"
full_name = f"{first_name} {last_name}"
print(full_name)  # Output: John Doe

✍️ Practice Exercises¶

Create variables for your name, age, height (in meters), and whether you like programming
Print all these variables using f-strings
Create a variable called temperature and use it in an if-else statement to check if it’s hot (> 30) or cold
Create variables for a product (name, price, quantity) and calculate the total cost

🔍 Common Mistakes¶

Forgetting quotes around strings: name = Alice ❌ should be name = "Alice" ✅
Using spaces in variable names: first name = "John" ❌ should be first_name = "John" ✅
Starting variable names with numbers: 1st_name ❌ should be first_name ✅

📝 Variable Naming Rules¶

Can contain letters, numbers, and underscores
Must start with a letter or underscore
Case-sensitive (age and Age are different)
Use snake_case for multi-word variables: first_name, student_count

🚀 Try It Yourself¶

Modify main.py to create variables about yourself and print them in creative ways!

🎓 Key Takeaways from Video¶

Variables store data values that can be reused
Use if-elif-else for conditional logic
Follow along with the video for hands-on practice

💡 These points cover the main concepts from the video tutorial to help reinforce your learning.

🔗 Next Chapter¶

Continue to Chapter 3: Type Casting to learn how to convert between data types!