Changing sets — Python: Dictionaries and Sets

Sets in Python are mutable. You can add and remove elements from them using the add, discard and remove methods:

s = set()
s.add(1)
s.add(2)
s.add(2)
s  # {1, 2}
s.discard(1)
s  # {2}
s.discard(1)
s  # {2}
s.remove(1)  # KeyError: 1