Python Sets

Creating sets

Sets hold unique items only. Duplicates are automatically removed.

s = {1, 2, 3, 2, 1}
print(s)  # {1, 2, 3}

Set operations

Union, intersection, and difference let you combine sets.

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

Try it yourself

Run the example below. Edit it and see what changes.

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

Common mistakes

• ⚠Sets are unordered — you cannot access items by index.
• ⚠Use set() for an empty set, not {} (that creates a dict).