Sets support the operations from maths, each with an operator and a method name:

Operation	Operator	Gives
union	`a \| b`	everything in either
intersection	`a & b`	only what is in both
difference	`a - b`	in a but not in b
symmetric difference	`a ^ b`	in one or the other, not both

maths = {"Ada", "Alan", "Grace", "Emmy"}
music = {"Grace", "Clara", "Alan"}
print("Either club:", sorted(maths | music))
print("Both clubs:", sorted(maths & music))
print("Maths only:", sorted(maths - music))
print("Just one club:", sorted(maths ^ music))

The method versions read like English and also accept lists: maths.union(["Kim"]), maths.intersection(music), maths.difference(music).

You can also ask whether one set is completely inside another: small <= big (or small.issubset(big)).