What Is a Loop in Python?

A loop in Python is a way to repeat code.

This is useful when you want to do the same task more than once. Instead of writing the same line again and again, you can write a loop once and let Python repeat it for you.

Python mainly has two loop types:

for loops
while loops

This page gives the basic idea of loops. It does not fully teach loop syntax.

Quick example

for number in [1, 2, 3]:
    print(number)

This loop prints each number in the list.

The indented line is the code that repeats. It runs once for each value.

Output:

1
2
3

What a loop means

A loop is a way to repeat code.

Here is the main idea:

You want to perform the same action multiple times
You write that action once inside a loop
Python runs it again for each repetition

Each time the loop runs is called an iteration.

For example, if a loop prints three items, that loop has three iterations.

Why loops are useful

Loops are useful because they help you avoid repeated code.

They are commonly used for tasks like:

working through items in a list
reading characters in a string
reading lines from a file
counting through a range of numbers

Loops also make code easier to update later. If the repeated step needs to change, you usually only change it in one place.

The main loop types in Python

Python has two main loop types.

`for` loop

A for loop repeats once for each item in a sequence.

That sequence might be:

a list
a string
a range()
other iterable values

Beginners often start with for loops because they are usually easier to read.

If you want a full lesson, see Python for loops explained.

`while` loop

A while loop repeats as long as a condition stays True.

This is useful when you do not know exactly how many times the loop should run.

For a full beginner guide, see Python while loops explained.

Simple example of a loop

Here is a small for loop:

for number in [1, 2, 3]:
    print(number)

What happens here:

for number in [1, 2, 3]: tells Python to go through the list one item at a time
print(number) is the repeated action
The indentation shows which line belongs to the loop

Expected output:

1
2
3

If the print(number) line was not indented, it would not be part of the loop. If indentation is confusing, read Python indentation rules and why they matter.

When to use a loop

Use a loop when you need to repeat a step.

Common examples:

Loop through items in a list
Repeat until the user enters valid input
Read lines from a file one by one
Count through a range of numbers

For example, if you want to process each item in a list, a loop is the natural tool. A good next step is how to loop through a list in Python.

You will also often see loops used with the range() function when counting numbers.

Important beginner idea

There are a few important things to understand early.

A loop can run many times
A loop can also run zero times
Indentation matters because it defines the repeated block
A while loop can become infinite if its condition never becomes False

For example, this while loop never stops:

while True:
    print("loop running")

This is called an infinite loop.

A while loop usually needs something to change so the condition eventually becomes false.

Also, be careful when changing loop variables or counting values. Small mistakes can cause bugs or make a loop behave in unexpected ways.

What this page should not cover in depth

This page is only a glossary-style definition.

It does not fully teach:

full for loop syntax
full while loop syntax
nested loops
break
continue

If you want to go further, read:

Common mistakes

Beginners often run into these problems:

Confusing a loop with an if statement
Thinking loops always run forever
Forgetting that indentation controls which lines repeat
Using a while loop without changing the condition
Not realizing that for loops usually go through a sequence

If you are not sure what a loop is doing, simple print() statements can help you debug it.

Examples:

print(item)
print(count)
print("loop running")

These help you see:

whether the loop is running
which value is being processed
how a counter is changing

FAQ

What is a loop in simple words?

A loop is code that repeats the same steps multiple times.

What are the two main loops in Python?

Python mainly uses for loops and while loops.

When should I use a for loop?

Use a for loop when you want to go through items like a list, string, or range.

When should I use a while loop?

Use a while loop when code should keep running until a condition changes.

Can a loop run forever?

Yes. A while loop can run forever if the condition never becomes false.