Set

Learn unique-element sets with {1, 2, 3}.

A set is an unordered, unique collection. It is written with curly braces:

fruits = {"apple", "banana", "cherry"}
print(len(fruits))  # 3

A set has two key properties: item order does not matter, and each item appears only once. This makes it handy for deduplication.

An empty set is created with set(); {} is an empty dict, not a set.

Set operations

Sets support mathematical set operations: union (|), intersection (&), difference (-):

a = {1, 2, 3}
b = {3, 4, 5}
print(a | b)  # {1, 2, 3, 4, 5}
print(a & b)  # {3}
print(a - b)  # {1, 2}

These operations are fast and readable. Membership tests with in are much faster than lists.

Assign the list [1, 2, 2, 3, 3, 3] to nums. Assign set(nums) to unique. Then print print(sorted(unique)).

Show example solution

nums = [1, 2, 2, 3, 3, 3]
unique = set(nums)
print(sorted(unique))

Avoid duplicates in a set

unique = {1, 2, 2, 3, 3, ____}

Show answer

unique = {1, 2, 2, 3, 3, 3}

Next lesson: Dict basics