# List Remove Duplicates

## Exercise 14 (and Solution)

Write a program (function!) that takes a list and returns a new list that contains all the elements of the first list minus all the duplicates.

Extras:

• Write two different functions to do this - one using a loop and constructing a list, and another using sets.
• Go back and do Exercise 5 using sets, and write the solution for that in a different function.

## Discussion

Concepts for this week:

• Sets

### Sets

In mathematics, a set is a collection of elements where no element is repeated. This becomes useful because if you know your data is stored in a set, you are guaranteed to have unique elements.

## Features of sets

• Sets are not ordered. This means that there is no “first element” or “last element.” There are just “elements”. You cannot ask a set for it’s “next element”.
• There are no repeat elements in sets.
• You can convert between sets and lists very easily.

## In Python

In Python, you make and use a set with the `set()` keyword. For example:

And the output will be;

You can do to a set almost anything you can do to a list (except ask for things like “the third element”). See the Python documentation about sets to get a full list of things you can do to sets.

You can convert from a list to a set and a set to a list pretty easily:

And the result of this will be:

## Happy coding!

Forgot how to submit exercises?