Slice view

The default list slice in Python creates a copy. It may be undesirable if a slice is too big to be copied, you want a slice to reflect changes in the list, or even want to modify a slice to affect the original object.

To solve the problem with copying a lot of data, one can use itertools.islice. It lets you iterate over the part of the list, but doesn't support indexing or modification.

The way to have a class for modifiable slices is to create it. Luckily Python provides the suitable abstract base class: collections.abc.MutableSequence (just collections.MutableSequence in Python 2). You only need to override __getitem__, __setitem__, __delitem__, __len__ and insert.

The example below doesn't support deletion and inserting, but supports slicing slices and modifications.