Python For Loop

At CIIT Training Institute, loops are taught using practical programming examples so that students can understand not only the syntax but also where loops are actually used in real applications.

The for loop is one of the most commonly used looping statements in Python. It is useful when we want to process multiple values one by one.

What is a For Loop?

A for loop executes a block of code once for each item in an iterable object.

An iterable can be:

• List
• Tuple
• String
• Set
• Dictionary
• Range

Instead of writing the same code multiple times, we can use a loop.

For Loop Concept

Suppose we have three students:

students = ["Sam", "Rahul", "Priya"]

Instead of writing three separate print statements, we can use a for loop.

The loop continues until all items in the collection have been processed.

For Loop Syntax

for variable in sequence:
    # code to execute

Example

students = ["Sam", "Rahul", "Priya"]

for student in students:
    print(student)

Output

Sam
Rahul
Priya

The variable student receives one item at a time from the list.

Iterating Over a List

A for loop is commonly used to process every item inside a list.

courses = [
    "Python",
    ".NET",
    "Java",
    "Data Science"
]

for course in courses:
    print(course)

Output

Python
.NET
Java
Data Science

Iterating Over a String

A string is also iterable. The loop processes one character at a time.

name = "SAM"

for character in name:
    print(character)

Output

S
A
M

Iterating Over a Tuple

technologies = ("Python", "Django", "Flask")

for technology in technologies:
    print(technology)

Each tuple element is accessed one by one.

Iterating Over a Set

skills = {"Python", "SQL", "Git"}

for skill in skills:
    print(skill)

A set can also be iterated using a for loop. Remember that sets do not guarantee a meaningful element order.

For Loop With Dictionary

Dictionaries contain key-value pairs. We can iterate through keys, values, or both.

1. Iterate Through Keys

student = {
    "name": "Sam",
    "course": "Python",
    "city": "Pune"
}

for key in student:
    print(key)

2. Iterate Through Values

for value in student.values():
    print(value)

3. Iterate Through Key and Value

for key, value in student.items():
    print(key, ":", value)

Output

name : Sam
course : Python
city : Pune

range() With For Loop

The range() function is frequently used when we want to repeat something a specific number of times.

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

Output

0
1
2
3
4

range(start, stop)

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

Output

1
2
3
4
5

Here, 1 is the starting value and 6 is the stopping value. Since the stop value is excluded, the loop ends at 5.

range(start, stop, step)

The third parameter specifies how much the value should change after every iteration.

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

Output

1
3
5
7
9

Here the loop increases the value by 2 after every iteration.

Reverse Iteration

A negative step can be used to iterate backwards.

for number in range(5, 0, -1):
    print(number)

Output

5
4
3
2
1

enumerate() Function

enumerate() allows us to access both the index and the value while looping.

courses = ["Python", ".NET", "Java"]

for index, course in enumerate(courses):
    print(index, course)

Output

0 Python
1 .NET
2 Java

We can also start the index from another number.

for index, course in enumerate(courses, start=1):
    print(index, course)

1 Python
2 .NET
3 Java

Nested For Loop

A loop inside another loop is called a nested loop.

for i in range(1, 4):

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

The inner loop runs completely for every iteration of the outer loop.

Example: Multiplication Table

number = 5

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

Output

5 x 1 = 5
5 x 2 = 10
5 x 3 = 15
...
5 x 10 = 50

break Inside For Loop

The break statement immediately stops the loop.

for number in range(1, 10):

    if number == 5:
        break

    print(number)

Output

1
2
3
4

As soon as number == 5, the loop stops.

continue Inside For Loop

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

for number in range(1, 6):

    if number == 3:
        continue

    print(number)

Output

1
2
4
5

Number 3 is skipped, but the loop continues.

else With For Loop

Python also allows an else block with a for loop.

The else block executes when the loop completes normally without encountering break.

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

Output

1
2
3
Loop completed

Example With break

for number in range(1, 6):

    if number == 3:
        break

    print(number)

else:
    print("Loop completed")

Output:

1
2

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

Example: CIIT Student Courses 📩🤓

Suppose CIIT has a list of courses and we want to display each course.

courses = [
    "Python Full Stack",
    ".NET Full Stack",
    "Java Full Stack",
    "Data Science",
    "Data Analytics"
]

for course in courses:
    print("Available Course:", course)

Output

Available Course: Python Full Stack
Available Course: .NET Full Stack
Available Course: Java Full Stack
Available Course: Data Science
Available Course: Data Analytics

This is a simple example of how loops can be used to process multiple records.

Example: Calculate Sum 📩

numbers = [10, 20, 30, 40, 50]

total = 0

for number in numbers:
    total = total + number

print("Total =", total)

Output

Total = 150

The loop processes every number and adds it to total.

Example: Filter Even Numbers 🫠📩

numbers = [10, 15, 20, 25, 30, 35]

for number in numbers:

    if number % 2 == 0:
        print(number)

Output

10
20
30

The modulo operator % is used to check whether a number is divisible by 2.

Common Mistakes in For Loop

Important: Loop Variable

The loop variable automatically receives the next item from the iterable.

students = ["Sam", "Rahul", "Priya"]

for student in students:
    print(student)

Here student changes automatically:

1. First iteration → Sam
2. Second iteration → Rahul
3. Third iteration → Priya

We normally should not manually modify the loop variable to control the loop.

For Loop vs While Loop

CIIT Practice Tasks

1. Create a list of 5 student names and print every student using a for loop.
2. Print numbers from 1 to 20 using range().
3. Print all even numbers between 1 and 50.
4. Create a multiplication table program where the user enters a number.
5. Create a list of course names and display their index and name using enumerate().
6. Create a list of numbers and calculate their total using a for loop.