Looping Statements in Python

Complete Tutorial with Examples and Output

1. Introduction to Looping

Looping is a programming technique used to execute a block of statements repeatedly. Instead of writing the same statement many times, a loop allows the programmer to execute it automatically.

For example, if we want to print numbers from 1 to 5, we can use a loop instead of writing five separate print() statements.

Start → Check Condition → Execute Block → Update → Repeat

Python mainly provides two types of loops:

for loop
while loop

Python also provides loop-control statements such as break, continue and pass.

2. for Loop

A for loop is used to iterate over a sequence such as a list, tuple, string, range, or other iterable object.

Syntax

for variable in sequence:
    statement

Example

for i in range(1, 6):
    print(i)

Output

3. range() Function

The range() function is commonly used with a for loop. It generates a sequence of numbers.

Example 1 – range(stop)

for i in range(5):
    print(i)

Output

The stop value 5 is not included.

Example 2 – range(start, stop)

for i in range(2, 7):
    print(i)

Output

Example 3 – range(start, stop, step)

for i in range(2, 11, 2):
    print(i)

Output

4. Looping Through a String

A for loop can be used to access each character of a string.

word = "Python"

for ch in word:
    print(ch)

Output

P
y
t
h
o
n

5. Looping Through a List

subjects = ["C", "Python", "Java", "DBMS"]

for subject in subjects:
    print(subject)

Output

C
Python
Java
DBMS

6. Looping Through a Tuple

numbers = (10, 20, 30, 40)

for n in numbers:
    print(n)

Output

7. while Loop

A while loop repeatedly executes a block of code as long as its condition remains True.

Syntax

while condition:
    statement

Example

i = 1

while i <= 5:
    print(i)
    i = i + 1

Output

8. Working of a while Loop

Initialize variable

↓

Check condition

↓

Condition True?

↓

Execute statements

↓

Update variable

↓

Check condition again

↓

Condition False → Exit Loop

9. Infinite Loop

An infinite loop occurs when the loop condition never becomes False.

For example:

while True:
    print("Hello")

This loop continues indefinitely until it is stopped.

Important: Make sure that a while loop has a suitable condition or update so that it can eventually terminate when required.

10. break Statement

The break statement immediately terminates the loop.

Example

for i in range(1, 10):
    if i == 5:
        break
    print(i)

Output

When i becomes 5, the break statement terminates the loop.

11. continue Statement

The continue statement skips the remaining statements in the current iteration and moves to the next iteration.

Example

for i in range(1, 6):
    if i == 3:
        continue
    print(i)

Output

The value 3 is skipped.

12. pass Statement

The pass statement does nothing. It is useful as a placeholder when a statement is syntactically required but no action is needed yet.

for i in range(5):
    pass

print("Loop completed")

Output

Loop completed

13. Nested Loops

A loop placed inside another loop is called a nested loop.

Example

for i in range(1, 4):
    for j in range(1, 4):
        print(i, j)

Output

14. Creating a Multiplication Table

Nested loops and the multiplication operator can be used to generate multiplication tables.

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

for i in range(1, 11):
    print(number, "x", i, "=", number * i)

Sample Output

Enter a number: 5
5 x 1 = 5
5 x 2 = 10
5 x 3 = 15
5 x 4 = 20
5 x 5 = 25
5 x 6 = 30
5 x 7 = 35
5 x 8 = 40
5 x 9 = 45
5 x 10 = 50

15. Sum of Numbers Using for Loop

total = 0

for i in range(1, 6):
    total = total + i

print("Sum =", total)

Output

Sum = 15

16. Printing Even Numbers

for i in range(1, 11):
    if i % 2 == 0:
        print(i)

Output

17. Printing Odd Numbers

for i in range(1, 11):
    if i % 2 != 0:
        print(i)

Output

18. Practical Example – Factorial

The factorial of a positive integer n is:

n! = n × (n − 1) × (n − 2) × ... × 1

Python Program

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

factorial = 1

for i in range(1, n + 1):
    factorial = factorial * i

print("Factorial =", factorial)

Sample Output

Enter a number: 5
Factorial = 120

19. Practical Example – Reverse a Number

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

reverse = 0

while number > 0:
    digit = number % 10
    reverse = reverse * 10 + digit
    number = number // 10

print("Reverse =", reverse)

Sample Output

Enter a number: 12345
Reverse = 54321

20. Practical Example – Count Digits

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

count = 0

if number == 0:
    count = 1
else:
    while number != 0:
        number = number // 10
        count = count + 1

print("Number of digits =", count)

Sample Output

Enter a number: 98765
Number of digits = 5

21. Practical Example – Check Prime Number

A prime number is a number greater than 1 that has no positive divisors other than 1 and itself.

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

if number < 2:
    print("Not a prime number")
else:
    is_prime = True

    for i in range(2, number):
        if number % i == 0:
            is_prime = False
            break

    if is_prime:
        print("Prime number")
    else:
        print("Not a prime number")

Sample Output

Enter a number: 17
Prime number

22. Practical Example – Fibonacci Series

The Fibonacci series starts with 0 and 1, and each subsequent number is the sum of the previous two numbers.

n = int(input("Enter number of terms: "))

a = 0
b = 1

for i in range(n):
    print(a, end=" ")
    a, b = b, a + b

Sample Output

Enter number of terms: 8
0 1 1 2 3 5 8 13

23. Practical Example – Star Pattern

Nested loops can be used to generate patterns.

for i in range(1, 6):
    for j in range(i):
        print("*", end=" ")
    print()

Output

* 
* * 
* * * 
* * * * 
* * * * *

24. Looping with enumerate()

The enumerate() function provides both the index and the value while iterating through a sequence.

subjects = ["C", "Python", "Java"]

for index, subject in enumerate(subjects):
    print(index, subject)

Output

0 C
1 Python
2 Java

25. Looping with zip()

The zip() function can be used to iterate over multiple sequences at the same time.

names = ["Rahul", "Amit", "Riya"]
marks = [85, 90, 78]

for name, mark in zip(names, marks):
    print(name, mark)

Output

Rahul 85
Amit 90
Riya 78

26. else with a Loop

Python allows an else block to be associated with a loop. For a for or while loop, the else block executes when the loop finishes normally rather than being terminated by break.

Example

for i in range(1, 4):
    print(i)
else:
    print("Loop completed")

Output

1
2
3
Loop completed

27. Loop else with break

for i in range(1, 6):
    if i == 3:
        break
    print(i)
else:
    print("Loop completed")

Output

1
2

The else block does not execute because the loop was terminated using break.

28. for Loop vs while Loop

for Loop	while Loop
Used to iterate over a sequence or iterable	Runs while a condition is True
Often used when the number of iterations is known	Useful when repetition depends on a condition
Commonly used with `range()`	Requires careful condition/update handling
`for i in range(5):`	`while condition:`

29. Loop Control Statements

Statement	Purpose
`break`	Terminates the loop immediately
`continue`	Skips the current iteration
`pass`	Does nothing; acts as a placeholder

30. Common Errors in Loops

Forgetting to update a while-loop variable: This can result in an infinite loop.
Incorrect indentation: Python uses indentation to identify the loop body.
Incorrect range: Remember that the stop value in range() is excluded.
Unnecessary nested loops: Too many nested loops can make a program slower and harder to understand.
Incorrect use of break: Make sure break is used only when the loop should terminate.

31. General Loop Flow

Start

↓

Initialize

↓

Check Condition / Get Next Item

↓

Execute Loop Body

↓

Update / Get Next Item

↓

Repeat

↓

Exit Loop

32. Summary

Looping is one of the most important concepts in Python programming. It allows a programmer to execute statements repeatedly without writing the same code again and again.

for loops are commonly used to iterate over sequences and iterables.
while loops execute while a condition remains True.
range() is frequently used with for loops.
Nested loops allow one loop to execute inside another loop.
break terminates a loop.
continue skips the current iteration.
pass acts as a placeholder.
enumerate() provides index and value while iterating.
zip() allows multiple sequences to be processed together.

Created by Bijan Krishna Paul

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Wednesday, September 9, 2026

LOOP

Looping Statements in Python

1. Introduction to Looping

2. for Loop

Syntax

Example

Output

3. range() Function

Example 1 – range(stop)

Output

Example 2 – range(start, stop)

Output

Example 3 – range(start, stop, step)

Output

4. Looping Through a String

Output

5. Looping Through a List

Output

6. Looping Through a Tuple

Output

7. while Loop

Syntax

Example

Output

8. Working of a while Loop

9. Infinite Loop

10. break Statement

Example

Output

11. continue Statement

Example

Output

12. pass Statement

Output

13. Nested Loops

Example

Output

14. Creating a Multiplication Table

Sample Output

15. Sum of Numbers Using for Loop

Output

16. Printing Even Numbers

Output

17. Printing Odd Numbers

Output

18. Practical Example – Factorial

Python Program

Sample Output

19. Practical Example – Reverse a Number

Sample Output

20. Practical Example – Count Digits

Sample Output

21. Practical Example – Check Prime Number

Sample Output

22. Practical Example – Fibonacci Series

Sample Output

23. Practical Example – Star Pattern

Output

24. Looping with enumerate()

Output

25. Looping with zip()

Output

26. else with a Loop

Example

Output

27. Loop else with break

Output

28. for Loop vs while Loop

29. Loop Control Statements

30. Common Errors in Loops

31. General Loop Flow

32. Summary

Created by Bijan Krishna Paul

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