# Python While Loop Exercises

Let’s check out some exercises that will help understand While Loops better.

#### Exercise 9-a

Write a while loop that adds all the numbers up to 100 (inclusive).

One of the key aspect of writing while loops is watching your counters. For instance, when you type while counter < 100:

If you don’t increase counter in every loop it will create an infinite loop as counter will stay the same and always below 100. Eventually you’ll get a runtime error.

So defining i before the loop:
counter = 0

And increasing i inside the loop:
counter = counter+1

are key points in most while loops.

This can be confusing for absolutely new programmers but you also need another counter which adds up the numbers during the iteration.

With some repetition and pondering you will definitely get a grip of while loops, it’s normal to struggle with them slightly more than for loops which usually doesn’t have to bother with counters for the loop to function properly.

So,
total = 0
before the loop;

and,
total = total+counter
inside the loop will ensure that total adds each number to the sum along the way during the iteration.

`while counter <= 100:    total= total+counter     counter= counter+1`

#### Exercise 9-b

Using a `while` loop, `len` function, an `if` statement and the `str()` function; iterate through the given list and if there is a 100, assign a notification message to the variable `my_message` with the index of 100.
i.e.: "There is a 100 at index no: 5"

i = 0

To make sure you go through the list you can construct your while loop as:
while i < len(lst)

Most important thing to remember, so that you don’t get an error is to increase i in each iteration as:
i = i+1

Inside your while loop, you can use an if statement as such:

if lst[i] == 100:
…

Besides being the counter i is being used as the index throughout the list and lst[i]  is the value of elements in the list at index: i

```message = ""
i = 0
while i < len(lst):
if lst[i] == 100:
my_message = "There is a 100 at index no: " + str(i)
i = i+1```