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.
- 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.
Concepts for this week:
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, 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:
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