Khalid Ahmad Khattak

Lesson 3 – Variables

A variable is a name used to store information in a program. Think of it as a box with a label. The label is the variable name, and the information inside the box is the value. Your program can open the box at any time to read or change the value stored inside.

Why Do We Use Variables?

Variables allow your program to remember information and use it again later. Instead of writing the same number or text repeatedly, you store it once in a variable.

Example 1: Storing Text

name = "Khalid"
print("Your name is:", name)
        

Output:

Your name is: Khalid

Example 2: Storing Whole Numbers

age = 38
print("Age:", age)
        

Age: 38

Example 3: Storing Decimal Values

height = 1.75
print("Height:", height)
        

Height: 1.75

Example 4: Changing a Variable

score = 10
print("Score:", score)

score = 20
print("Updated score:", score)
        

Score: 10
Updated score: 20
        

Example 5: Adding Variable Values

a = 5
b = 7
total = a + b
print("Total:", total)
        

Total: 12

Variable Naming Rules

• Must begin with a letter or underscore
• Cannot begin with a number
• No spaces allowed
• Case-sensitive (Age is different from age)
• Should not use Python keywords (such as if, for, class)

Quiz: Test Your Understanding

x = 4
x = x + 6