Source: 📖 Effective Python item 11

Slices do not modify the original list

When a slice is created, the original list object is preserved and a new list object is created.

my_list = [1, 2, 3, 4]
sliced = my_list[1:20]

print(my_list)	# unchanged
print(sliced)	# new list object

>>>
[1, 2, 3, 4]
[2, 3, 4]