Sets
Data structures4 min readLesson 3 of 3
A set stores unique items with no order.
python
letters = {"a", "b", "a"} # {'a', 'b'}
"a" in letters # fastSet algebra is the reason to reach for one:
python
a = {1, 2, 3}
b = {3, 4}
a | b # union {1, 2, 3, 4}
a & b # intersection {3}
a - b # difference {1, 2}Deduplicating a list is one line: list(set(items)). Remember the order is lost; use dict.fromkeys(items) when order matters.
Sets need hashable members, so a list of lists cannot become a set. Convert the inner lists to tuples first.