Are Python sets mutable?

Question

Are sets in Python mutable?

---

In other words, if I do this:

x = set([1, 2, 3])
y = x

y |= set([4, 5, 6])

Are x and

Answer 1

print x,y

and you see they both point to the same set:

set([1, 2, 3, 4, 5, 6]) set([1, 2, 3, 4, 5, 6])