They cannot contain any duplicate elements.
Their usefulness is associated with group membership tests and elimination of duplicate elements.
set1 = set() # Defining an empty set
set1 = {1,2,3}
set1.add(0)
set1.add(3) # Even if we add 3, since it already contains it, it will not be added
print(set1){0, 1, 2, 3}
ELIMINATING DUPLICATE elements from other Collections
list1 = [1,2,3,4,4,3,2,1] # This list contains repeated elements
c = set(list1) # we create a set (c) that has list1 as elements
list1 = list (c) # we regenerate (list1) with the content of (c)
print (list1) # And as we see the passage of elements through the set (c) has eliminated the duplicates[1, 2, 3, 4]