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Wednesday, September 9, 2026

Branching,

Branching Statements in Python

Complete Tutorial with Examples and Output

1. Introduction to Branching

Branching is a programming technique used to make decisions in a program. It allows a program to execute different blocks of code depending on whether a condition is True or False.

In Python, branching is mainly performed using:

  • if statement
  • if-else statement
  • if-elif-else statement
  • Nested if statements
Condition → True → Execute one block
Condition → False → Execute another block

2. if Statement

The if statement executes a block of code only when its condition is True.

Syntax

if condition:
    statement

Example

age = 20

if age >= 18:
    print("You are an adult.")

Output

You are an adult.

3. When the if Condition is False

If the condition is False, Python skips the indented block. 

age = 15

if age >= 18:
    print("You are an adult.")

print("Program completed.")

Output

Program completed.

4. if-else Statement

The if-else statement provides two possible execution paths. If the condition is True, the if block executes. Otherwise, the else block executes.

Syntax

if condition:
    statement1
else:
    statement2

Example

number = 10

if number > 0:
    print("Positive number")
else:
    print("Not a positive number")

Output

Positive number

5. Practical Example – Even or Odd

The modulus operator % can be used to determine whether a number is even or odd. 

number = int(input("Enter a number: "))

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

Sample Output

Enter a number: 24
Even number

6. Positive, Negative or Zero

When more than two possibilities exist, an if-elif-else structure can be used. 

number = int(input("Enter a number: "))

if number > 0:
    print("Positive")
elif number < 0:
    print("Negative")
else:
    print("Zero")

Sample Output

Enter a number: -8
Negative

7. if-elif-else Statement

The elif keyword means "else if". It is used when a program needs to test multiple conditions.

Syntax

if condition1:
    statement1
elif condition2:
    statement2
elif condition3:
    statement3
else:
    statement4

Example

marks = 75

if marks >= 90:
    print("Grade A+")
elif marks >= 80:
    print("Grade A")
elif marks >= 70:
    print("Grade B")
else:
    print("Grade C")

Output

Grade B

8. Practical Example – Student Grade

marks = int(input("Enter marks: "))

if marks >= 90:
    grade = "A+"
elif marks >= 80:
    grade = "A"
elif marks >= 70:
    grade = "B"
elif marks >= 60:
    grade = "C"
elif marks >= 50:
    grade = "D"
else:
    grade = "F"

print("Grade:", grade)

Sample Output

Enter marks: 85
Grade: A

9. Nested if Statement

A nested if statement means placing one if statement inside another if statement.

Example

age = 20
has_id = True

if age >= 18:
    if has_id:
        print("Entry allowed")
    else:
        print("ID required")
else:
    print("Entry not allowed")

Output

Entry allowed

10. Branching Using Comparison Operators

Conditions commonly use comparison operators.

Operator Meaning Example
== Equal to a == b
!= Not equal to a != b
> Greater than a > b
< Less than a < b
>= Greater than or equal a >= b
<= Less than or equal a <= b

11. Branching Using Logical Operators

Logical operators allow multiple conditions to be combined.

  • and – both conditions must be True
  • or – at least one condition must be True
  • not – reverses the Boolean result

Example using and

age = 20
marks = 80

if age >= 18 and marks >= 50:
    print("Eligible")
else:
    print("Not eligible")

Output

Eligible

12. Using the or Operator

day = "Sunday"

if day == "Saturday" or day == "Sunday":
    print("Holiday")
else:
    print("Working day")

Output

Holiday

13. Using the not Operator

logged_in = False

if not logged_in:
    print("Please login first")

Output

Please login first

14. Practical Example – Find Largest of Two Numbers

a = int(input("Enter first number: "))
b = int(input("Enter second number: "))

if a > b:
    print("Largest =", a)
elif b > a:
    print("Largest =", b)
else:
    print("Both numbers are equal")

Sample Output

Enter first number: 25
Enter second number: 40
Largest = 40

15. Practical Example – Largest of Three Numbers

a, b, c = map(int, input("Enter three numbers: ").split())

if a >= b and a >= c:
    largest = a
elif b >= a and b >= c:
    largest = b
else:
    largest = c

print("Largest =", largest)

Sample Output

Enter three numbers: 25 60 40
Largest = 60

16. Practical Example – Leap Year

A year is a leap year when it is divisible by 400, or when it is divisible by 4 but not divisible by 100. 

year = int(input("Enter year: "))

if year % 400 == 0:
    print("Leap year")
elif year % 100 == 0:
    print("Not a leap year")
elif year % 4 == 0:
    print("Leap year")
else:
    print("Not a leap year")

Sample Output

Enter year: 2024
Leap year

17. Practical Example – Voting Eligibility

age = int(input("Enter your age: "))

if age >= 18:
    print("You are eligible to vote.")
else:
    print("You are not eligible to vote.")

Sample Output

Enter your age: 20
You are eligible to vote.

18. Practical Example – Simple Login Check

username = input("Enter username: ")
password = input("Enter password: ")

if username == "admin" and password == "1234":
    print("Login successful")
else:
    print("Invalid username or password")

Sample Output

Enter username: admin
Enter password: 1234
Login successful

19. Practical Example – Simple Calculator

Branching can be used to create a simple calculator by selecting an operation. 

a = float(input("Enter first number: "))
b = float(input("Enter second number: "))

operator = input("Enter operator (+, -, *, /): ")

if operator == "+":
    print("Result =", a + b)
elif operator == "-":
    print("Result =", a - b)
elif operator == "*":
    print("Result =", a * b)
elif operator == "/":
    if b != 0:
        print("Result =", a / b)
    else:
        print("Cannot divide by zero")
else:
    print("Invalid operator")

Sample Output

Enter first number: 20
Enter second number: 5
Enter operator (+, -, *, /): *
Result = 100.0

20. Importance of Indentation

Python uses indentation to identify blocks of code. Statements belonging to an if, elif, or else block must be indented consistently.

Correct Example

age = 20

if age >= 18:
    print("Adult")

Important

The statement print("Adult") is indented because it belongs to the if block.

21. Conditional Expression

Python also provides a compact form of branching called a conditional expression.

Syntax

value_if_true if condition else value_if_false

Example

age = 20

status = "Adult" if age >= 18 else "Minor"

print(status)

Output

Adult

22. Flow of Branching

Start

↓

Evaluate Condition

↓

True → Execute True Block

or

False → Execute False / Next Condition

↓

Continue Program

23. Common Errors in Branching

  • Forgetting the colon:
    if age >= 18:
  • Incorrect indentation: Statements inside the branch must be properly indented.
  • Using = instead of ==:
    = is assignment, while == checks equality.
  • Incorrect condition order: In an if-elif structure, conditions should be arranged carefully.

24. Branching Statements Quick Reference

Statement Purpose
if Execute code when a condition is True
if-else Choose between two alternatives
if-elif-else Choose among multiple alternatives
Nested if Place one decision inside another
Conditional expression Compact one-line decision

25. Summary

Branching is an important part of Python programming because it allows a program to make decisions based on conditions.

The main branching structures are if, if-else, if-elif-else, and nested if statements. Comparison operators and logical operators are commonly used to construct branching conditions.

Branching is used in many practical applications including student grading, login systems, voting eligibility, calculators, billing systems, validation, menu-driven programs and decision-making systems.

Created by Bijan Krishna Paul

Computer Science • Python Programming • Data Science

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