import copy bus1 = Bus(['Alice', 'Bill', 'Claire', 'David']) bus2 = copy.copy(bus1) bus3 = copy.deepcopy(bus1) id(bus1), id(bus2), id(bus3) (4301498296, 4301499416, 4301499752) ➊ bus1.drop('Bill') bus2.passengers ['Alice', 'Claire', 'David'] ➋ id(bus1.passengers), id(bus2.passengers), id(bus3.passengers) (4302658568, 4302658568, 4302657800) ➌ bus3.passengers ['Alice', 'Bill', 'Claire', 'David']