Python set() built-in function
From the Python 3 documentation
Return a new set object, optionally with elements taken from iterable. set is a built-in class. See set and Set Types — set, frozenset for documentation about this class.
Introduction
The set() constructor creates a new set. A set is an unordered collection of unique elements. You can create an empty set, or create a set from an iterable.
Examples
Create an empty set:
my_set = set()
print(my_set) # Output: set()
Create a set from a list (duplicates are removed):
my_list = [1, 2, 2, 3, 3, 3]
my_set = set(my_list)
print(my_set) # Output: {1, 2, 3}