How to remove set element in copied object

Question

The following code removes a set element from a copied dictionary, yet both dictionaries are changed. How can have dic1 remain unchanged?

dic1 = {'a': set([1,2])}
dic2 = dic1.copy()
dic2['a'].discard(1)

Answer 1

learn about copy — Shallow and deep copy operations to understand why copy doesn't work, but deepcopy works

Answer 2

import copy

dic1 = {'a': set([1,2])}
dic2 = copy.deepcopy(dic1)
dic2['a'].discard(1)