Variables and Data Types

Variables: Storing Data

Variables are like labeled boxes that store information. In Python, you create variables by simply assigning values - no special declaration needed!

Creating Variables

Python is dynamically typed, meaning you don't need to declare variable types:

# String (text)
name = "Alice"
message = 'Hello, World!'

# Numbers
age = 25
price = 19.99

# Boolean (True/False)
is_student = True
is_active = False

Python Data Types

1. Strings (str)

Text data enclosed in quotes:

first_name = "John"
last_name = 'Doe'
full_name = first_name + " " + last_name
print(full_name)  # John Doe

2. Integers (int)

Whole numbers (positive, negative, or zero):

score = 100
temperature = -5
count = 0

3. Floats (float)

Decimal numbers:

pi = 3.14159
price = 19.99
weight = 68.5

4. Booleans (bool)

True or False values (must be capitalized!):

is_student = True
is_complete = False
has_permission = True

Checking Data Types

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

name = "Python"
print(type(name))  # <class 'str'>

age = 25
print(type(age))   # <class 'int'>

price = 19.99
print(type(price)) # <class 'float'>

Variable Naming Rules

• ✅ Start with letter or underscore: name, _private
• ✅ Can contain letters, numbers, underscores: user_name, score2
• ✅ Case sensitive: Name ≠ name
• ❌ Can't start with number: 2name (invalid)
• ❌ Can't use Python keywords: if, for, class

Best Practices

• Use descriptive names: user_age not ua
• Use snake_case: user_name not userName
• Make names meaningful: total_score not ts