freeCodeCamp/guide/english/python/learn-about-python-sets/index.md

title
Learn About Python Sets

Sets in Python are a type of mutable but unordered data structure, which can only contain unique elements.

Creation:

set literal:

Curly brackets, {}, cannot be used to create an empty set:

>>> not_set = {}     # set constructor must be used to make empty sets.
>>> type(not_set)    # Empty curly brackets create empty dictionaries.
<class 'dict'>

You can only create an empty set by using the set() method.

>>> example_set = set()
>>> type(example_set)
<class 'set'>

However, if elements are included within the curly brackets, then it would be acceptable syntax to create a set.

>>> example_set_2 = {1, 2, 3}
>>> type(example_set_2)
<class 'set'>

Converting List to Set

If you want to convert a list to a set, you can do that by using the set() function. This will remove all duplicate values from the list.

>>> a = [11,2,2,6,6,4,8,9,9,7]
>>> a = set(a)
>>> print(a) # {2, 4, 6, 7, 8, 9, 11}