How to Create Loops in Python

Last Updated: February 7, 2023

In Python, and many other programming languages, you will need to loop commands several times, or until a condition is fulfilled. It is easy, and the loop itself only needs a few lines of code.

1

Open your shell or program.

This may be IDLE or Stani's Python Editor (SPE). Make sure all subprograms are off if using IDLE.

2

Write a for loop.

If you need to loop a definite amount of times, you need a for loop. This is the structure for a for loop:
- for i in range (0, 10):
- print "Hello World"

3

Write a while loop.

If you need something to loop forever, or until a condition is met, you need a while loop. A method for both is shown.
- while True:
- print "Hello World"

4

Make the while loop last until a condition is met.

This will loop forever, or until the program ends. True will always be True.
- while answer == "Yes" and grade == "6":
- As long as the variables answer and grade are Yes and 6,

5

Stop a loop.

If you need to stop a loop, use Ctrl-C. You can always kill the loop in task manager as well.

Community Q&A

Question

How do you do a nested loop?

Adam Blalock

Community Answer

Here is a loop within a loop in Python: x = [0,1,2,3,4], y= [10,11,12,13]. For i in x: For ii in y: print i + ii. (Make sure to do it as a single tab before the second "For" and two tabs for the "print" statement.)
Question

What about web development?

Community Answer

You need to learn about Django, the Python framework for web development.
Question

How do you use a while loop to repeat a calculator program?

Community Answer

First create a function. For example, if you wanted to square numbers 1 through 100 and print the results to the screen, I would write: def square(x): return x*x for i in range(1, 101): # stop = 101 because the stop value is not included. This will go from 1-100. print(square(i)).