# Python for Basic Data Analysis: 2.4 Functions - A Fun Exercise!

Get started on your learning journey towards data science using Python. Equip yourself with practical skills in Python programming for the purpose of basic data manipulation and analysis.

## A Fun Exercise!

Let's create a function that will help us check if a number is prime.

A number is prime if the number is only divisible by 1 and itself.

This function will take in 1 argument, N, which is the number we want to check. Next, it will go through all the numbers from 1 to N and perform modulo checks.

##### Try it yourself before looking at the answers!

1. In your function, you can use a for-loop together with if-else conditions

2. Make use of `%` in python to find out the remainder. To find the remainder of 3 divided by 2, we write `3%2`

3. Take the given number and find the remainder when divided by all numbers from 1 to itself. Check whether the conditions for a prime number is met.

4. When a given number is divisible by another number, it is not prime. Use `break` to stop a for-loop without returning anything

Take note on how the `else` lines up under `for` instead of `if`. We want the `for` loop to check all numbers 2 to N-1 before confirming that our number is prime. Should the `else` be alligned with `if` inside the `for` loop, we will be printing "is prime" before exhausting all possibilities.

`break` was introduced because once we have discovered that the number is not prime (i.e can be divided by a number that is not 1 and itself) we can stop checking and break out of the `for` loop.