L2·Control & Collections
🎯Sets
Unordered collections of unique hashables.
setunionintersection
§ 1Creation
{1,2,3} or set([1,2,3]). Empty set is set(), because {} is a dict.
§ 2Set algebra
a | b union, a & b intersection, a - b difference, a ^ b symmetric difference.
§ 3O(1) membership
x in s is average O(1) for sets and dicts, O(n) for lists.
Example
1a = {1,2,3,4}2b = {3,4,5,6}3print(a | b) # {1,2,3,4,5,6}4print(a & b) # {3,4}5print(a ^ b) # {1,2,5,6}Try it live · Python runs in your browser
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Checkpoint quiz
Question 1 / 2
What does {} create?