Are Python sets mutable?

Question

Are sets in Python mutable?

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In other words, if I do this:

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

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

Are x and

Answer 1

I don't think Python sets are mutable as mentioned clearly in book "Learning Python 5th Edition by Mark Lutz - Oreilly Publications"