Shallow copying a container in python builds a new instance of the container type, but the elements inside the container are just references to the same objects in the container prior to copying. This means that if you shallow copy a list for example, and update the index[0], both lists will be updated as they are the same object in memory, let's try it out:
items = [1,2,3,4,5] new_items = items.copy() items[0] = 10 items [10, 2, ...] new_items # [10, 2, ...]
...