Variables and Data Types

Variables are containers for storing data. Think of them as labeled boxes where you can put information.

Creating Variables

In Python, you create a variable by giving it a name and assigning a value:

name = "Alice"
age = 25
height = 5.6
is_student = True

Notice that we didn't have to declare the type - Python figures it out automatically!

Data Types

Python has several built-in data types:

Strings (str)

Text data, enclosed in quotes:

greeting = "Hello"
name = 'Bob'
message = """This is a
multi-line string"""

Integers (int)

Whole numbers:

count = 42
temperature = -10
year = 2024

Floats (float)

Decimal numbers:

pi = 3.14159
price = 19.99
percentage = 0.75

Booleans (bool)

True or False values:

is_active = True
has_permission = False

Checking Types

Use type() to check a variable's type:

x = 42
print(type(x))  # <class 'int'>

y = "hello"
print(type(y))  # <class 'str'>

Variable Naming Rules

1. Must start with a letter or underscore
2. Can contain letters, numbers, and underscores
3. Case-sensitive (name and Name are different)
4. Cannot use Python keywords (if, for, while, etc.)

# Good names
user_name = "Alice"
totalCount = 100
_private = "secret"

# Bad names (will cause errors)
# 2nd_place = "silver"  # Can't start with number
# my-variable = 5       # Can't use hyphens
# class = "Math"        # Can't use keywords

Practice

Try creating variables of different types and printing them:

# Your turn!
my_name = "Your Name"
my_age = 20
favorite_number = 7.5

print(f"Hi, I'm {my_name}!")
print(f"I'm {my_age} years old.")
print(f"My favorite number is {favorite_number}")

Note: The f before the string creates an "f-string" which lets you embed variables directly in text!