What is a set?

A set stores unique elements.

A set is a data structure that stores unique elements. An element is either in the set or not; there is no ordering.

Add, remove and search in a set are average O(1). Duplicates are automatically eliminated: the same element cannot be added twice.

Add and search

Elements are added to a set with add(item). contains(item) checks whether an element is in the set.

A set uses a hash table to provide O(1) average access. If the element already exists, add does nothing.

Write set_add(s, item). Add item to s, return s. Print {1, 2, 3} with print(set_add({1, 2}, 3)).

Show example solution

def set_add(s, item):
    # Add
    s.add(item)
    return s
print(sorted(set_add({1, 2}, 3)))

Add

Adding to a set is done with ____.

Show answer

Adding to a set is done with add.