Sets

Sets are unordered collections of unique, immutable items. The set itself is mutable, so you can add or remove elements.

Creating Sets

numbers = {1, 2, 3}
mixed = {1.0, "Hello", (1, 2, 3)}

from_list = set([1, 2, 2, 3])  # {1, 2, 3}

An empty set must be created with set():

empty = set()

Adding and Removing

s = {1, 3}
s.add(2)
s.update([2, 4, 5])

s.remove(4)   # raises KeyError if missing
s.discard(10) # no error if missing

Set Operations

a = {1, 2, 3, 4}
b = {3, 4, 5, 6}

print(a | b)  # union
print(a & b)  # intersection
print(a - b)  # difference
print(a ^ b)  # symmetric difference

Membership and Iteration

print(2 in a)  # True

for item in a:
    print(item)

Frozenset (Immutable Set)

f = frozenset([1, 2, 3])
# f.add(4)  # AttributeError

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