Ниже код демонстрирует разницу между присваиванием, мелкой копией с использованием метода копирования, мелкой копией с использованием (срез) [:] и глубокой копии. Ниже пример использует вложенные списки там, делая различия более очевидными.
from copy import deepcopy
########"List assignment (does not create a copy) ############
l1 = [1,2,3, [4,5,6], [7,8,9]]
l1_assigned = l1
print(l1)
print(l1_assigned)
print(id(l1), id(l1_assigned))
print(id(l1[3]), id(l1_assigned[3]))
print(id(l1[3][0]), id(l1_assigned[3][0]))
l1[3][0] = 100
l1.pop(4)
l1.remove(1)
print(l1)
print(l1_assigned)
print("###################################")
########"List copy using copy method (shallow copy)############
l2 = [1,2,3, [4,5,6], [7,8,9]]
l2_copy = l2.copy()
print(l2)
print(l2_copy)
print(id(l2), id(l2_copy))
print(id(l2[3]), id(l2_copy[3]))
print(id(l2[3][0]), id(l2_copy[3][0]))
l2[3][0] = 100
l2.pop(4)
l2.remove(1)
print(l2)
print(l2_copy)
print("###################################")
########"List copy using slice (shallow copy)############
l3 = [1,2,3, [4,5,6], [7,8,9]]
l3_slice = l3[:]
print(l3)
print(l3_slice)
print(id(l3), id(l3_slice))
print(id(l3[3]), id(l3_slice[3]))
print(id(l3[3][0]), id(l3_slice[3][0]))
l3[3][0] = 100
l3.pop(4)
l3.remove(1)
print(l3)
print(l3_slice)
print("###################################")
########"List copy using deepcopy ############
l4 = [1,2,3, [4,5,6], [7,8,9]]
l4_deep = deepcopy(l4)
print(l4)
print(l4_deep)
print(id(l4), id(l4_deep))
print(id(l4[3]), id(l4_deep[3]))
print(id(l4[3][0]), id(l4_deep[3][0]))
l4[3][0] = 100
l4.pop(4)
l4.remove(1)
print(l4)
print(l4_deep)
print("##########################")
print(l4[2], id(l4[2]))
print(l4_deep[3], id(l4_deep[3]))
print(l4[2][0], id(l4[2][0]))
print(l4_deep[3][0], id(l4_deep[3][0]))