import copy # this is the module to use
l1 = [[10,20,30], 1, 2, 3]
l2 = copy.deepcopy(l1) # create a copy using the deepcopy function from copy
l1.append(4) # append to list l1
l1[0].append(40) # modify the inner list of l1
print( l1 )
print( l2 )
Output
[[10, 20, 30, 40], 1, 2, 3, 4]
[[10, 20, 30], 1, 2, 3]