Set 集合

s = {1, 2, 3}
s.add(4)
s.remove(1)

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