Python for Loop: Purpose, Syntax, and Examples with Lists

1. What is a for loop?

A for loop in Python is used to execute a block of statements..

For example, suppose we have a list containing the names of four students:

students = ["Amit", "Ravi", "Neha", "Priya"]

If we want to print every student’s name, we could write separate print() statements for each name. This becomes inconvenient when the list contains many items.

The for loop makes this easier by taking the items from the list one by one and performing the required operation.

students = ["Amit", "Ravi", "Neha", "Priya"]

for student in students:
    print(student)

Output:

Amit
Ravi
Neha
Priya

2. Purpose of the for Loop

The main purpose of a for loop is to execute 1 or more statements in a program. for loop with list are explained in post. .

It is useful when:

• We want to access every item in a list.
• We want to perform the same operation on all list elements.
• We want to display all elements of a list.
• We want to calculate or process information from each element.

For example, consider the following list:

numbers = [10, 20, 30, 40]

for number in numbers:
    print(number * 2)

Output:

20
40
60
80

So, the important idea is:

3. Syntax of for Loop

The basic syntax of a Python for loop with a list is:

for variable in list_1:
    statement

For example:

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

for fruit in fruits:
    print(fruit)

In this example:

• for → Python keyword used to start the loop.
• fruit → Loop variable that stores one item from the list at a time.
• in → Python keyword used to take items from the list.
• fruits → The list whose items are processed one by one.
• : → Indicates the beginning of the loop body.
• print(fruit) → Statement executed for each item in the list_1.

4. How Does the for Loop Work?

Consider the following program:

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

for fruit in fruits:
    print(fruit)

The for loop takes the items from the fruits list one by one and stores each item in the loop variable fruit.

fruit = "Apple"
print(fruit)

fruit = "Mango"
print(fruit)

fruit = "Orange"
print(fruit)

5. Indentation in a for Loop

In Python, indentation is used to identify the statements that belong to the for loop.

For example:

students = ["Amit", "Ravi", "Neha"]

for student in students:
    print(student)
    print("Student name displayed")

Both print() statements are indented, so both statements are executed for every item in the list.

Output:

Amit
Student name displayed
Ravi
Student name displayed
Neha
Student name displayed

A statement without indentation is outside the loop.

students = ["Amit", "Ravi", "Neha"]

for student in students:
    print(student)

print("Loop completed")

Here, the last print() statement is outside the loop, so it executes only once after the loop has finished.

Output:

Amit
Ravi
Neha
Loop completed

Practice Programs with Different List Objects

A list can contain different types of objects such as Integer, Float, String and Boolean objects. Try the following simple programs.

numbers = [10, 20, 30]

for number in numbers:
    print(number)

numbers = [2, 4, 6]

for number in numbers:
    print(number * number)

values = [1.5, 2.5, 3.5]

for value in values:
    print(value)

values = [1.5, 2.5, 3.5]

for value in values:
    print(value + 1)

names = ["Amit", "Ravi", "Neha"]

for name in names:
    print(name)

names = ["amit", "ravi", "neha"]

for name in names:
    print(name.upper())

values = [True, False, True]

for value in values:
    print(value)

items = [10, 2.5, "Python", True]

for item in items:
    print(item)