Module 2.11 : Loops in Python

Introduction

In programming, many situations require performing the same task multiple times. Writing the same code repeatedly is inefficient and difficult to maintain.

Python solves this problem using Loops.

Loops allow a block of code to run repeatedly until a condition becomes False or a sequence is completed.

Loops are extremely important in Artificial Intelligence, Data Science, Machine Learning, Automation, and software development because they help process large amounts of data efficiently.

In this tutorial, you will learn Python loops, different types of loops, loop control statements, nested loops, and practical applications.

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Learning Objectives

• Understand loops in Python.
• Learn for loops.
• Understand while loops.
• Use nested loops.
• Understand break and continue statements.
• Build repetitive programs efficiently.

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What are Loops in Python?

Loops are control structures used to repeat a block of code multiple times.

Instead of writing repetitive code manually, a loop automatically executes instructions repeatedly.

Example without loops:

print("Python")
print("Python")
print("Python")

Using a loop:

for i in range(3):
    print("Python")

Output:

Python
Python
Python

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Why Loops are Important

Loops are important because they save time, reduce code repetition, and simplify programming logic.

Loops are widely used in:

• Data Processing
• Machine Learning Training
• Data Cleaning
• Automation Scripts
• Game Development
• Web Applications
• Artificial Intelligence Models

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Types of Loops in Python

Python mainly provides two types of loops:

• for loop
• while loop

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1. The for Loop

The for loop is used for iterating through sequences.

A sequence can be:

• List
• Tuple
• String
• Dictionary
• Range of numbers

Syntax

for variable in sequence:
    statement

Example Using Range

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

Output:

0
1
2
3
4

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Using range() Function

The range() function generates a sequence of numbers.

Single Parameter

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

Output:

0 1 2 3 4

Start and End Parameters

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

Output:

1
2
3
4
5

Step Parameter

for i in range(1,11,2):
    print(i)

Output:

1
3
5
7
9

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Looping Through Strings

A for loop can iterate through characters in a string.

word = "Python"

for letter in word:
    print(letter)

Output:

P
y
t
h
o
n

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Looping Through Lists

Lists are commonly used with loops.

fruits = ["Apple","Banana","Orange"]

for item in fruits:
    print(item)

Output:

Apple
Banana
Orange

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2. The while Loop

The while loop repeats code while a condition remains True.

Syntax

while condition:
    statement

Example

count = 1

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

Output:

1
2
3
4
5

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Infinite Loops

If the loop condition never becomes False, the loop runs forever.

This is called an Infinite Loop.

Example:

while True:
    print("Running")

This loop never stops.

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Nested Loops

A nested loop means placing one loop inside another loop.

Example

for i in range(3):

    for j in range(2):

        print(i,j)

Output:

0 0
0 1
1 0
1 1
2 0
2 1

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Loop Control Statements

Python provides loop control statements to modify loop behavior.

• break
• continue
• pass

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1. break Statement

The break statement immediately exits the loop.

for i in range(10):

    if i == 5:
        break

    print(i)

Output:

0
1
2
3
4

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2. continue Statement

The continue statement skips the current iteration.

for i in range(6):

    if i == 3:
        continue

    print(i)

Output:

0
1
2
4
5

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3. pass Statement

The pass statement is a placeholder that does nothing.

for i in range(3):

    pass

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Loops in Artificial Intelligence

Loops are extremely important in Artificial Intelligence and Machine Learning.

They are used for:

• Model Training
• Data Processing
• Feature Engineering
• Prediction Iteration
• Algorithm Execution

AI models often process thousands or millions of records using loops.

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Real-World Examples

Multiplication Table

number = 5

for i in range(1,11):

    print(number * i)

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Password Validation Example

attempts = 1

while attempts <= 3:

    print("Try Login")

    attempts += 1

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Python Example

numbers = [10,20,30,40]

for value in numbers:

    print(value)

Output:

10
20
30
40

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Interview Questions

1. What are loops in Python?

Loops are used to repeat a block of code multiple times.

2. Name two main loops in Python.

for loop and while loop.

3. What does the break statement do?

It immediately exits the loop.

4. What does continue do?

It skips the current iteration.

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Assignment

1. Create a for loop printing numbers from 1 to 10.
2. Create a while loop printing even numbers.
3. Print characters of a string using a loop.
4. Use break in a loop example.
5. Create a multiplication table program.

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Quiz

Q1. Which loop iterates through sequences?

• A. while
• B. for
• C. break
• D. pass

Answer: B. for

Q2. Which statement exits a loop immediately?

• A. continue
• B. pass
• C. break
• D. import

Answer: C. break

Q3. Which loop runs while a condition is True?

• A. while
• B. for
• C. def
• D. class

Answer: A. while

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Summary

In this tutorial, you learned Loops in Python. You explored for loops, while loops, nested loops, and loop control statements including break, continue, and pass.

Loops help automate repetitive tasks and are essential for Artificial Intelligence, Machine Learning, Data Science, and software development.

Next Tutorial

Tutorial 17: Functions in Python

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