Python Conditional Statements – Making Decisions in Programs

Introduction

Programs become powerful when they can make decisions.

Example:

• If student passes → show “Congratulations”
• If password is correct → login

This is done using conditional statements.

The if Statement

age = 18if age >= 18:
    print("You can vote")

Indentation is important.

if-else Statement

age = 16if age >= 18:
    print("You can vote")
else:
    print("You cannot vote")

if-elif-else

marks = 85if marks >= 90:
    print("Grade A")
elif marks >= 75:
    print("Grade B")
elif marks >= 60:
    print("Grade C")
else:
    print("Fail")

Nested Conditions

age = 20
citizen = Trueif age >= 18:
    if citizen:
        print("Eligible to vote")

Real Example: Login System

username = input("Enter username: ")
password = input("Enter password: ")if username == "admin" and password == "1234":
    print("Login Successful")
else:
    print("Invalid Credentials")

Checking Multiple Conditions

number = int(input("Enter number: "))if number % 2 == 0:
    print("Even")
else:
    print("Odd")

Common Mistakes

• Missing colon :
• Wrong indentation
• Using = instead of ==

Conclusion

You now know:

• if
• if-else
• elif
• Nested conditions

Next, we will learn loops.