Maybe it's time to add a new module for sequence-specific functions (seqtools?). It should contain at least two classes or fabric functions: 1. A view that represents a sliced subsequence. Lazy equivalent of seq[start:end:step]. This feature is implemented in third-party module dataview [1]. 2. A view that represents a linear sequence as 2D array. Iterating this view emits non-intersecting chunks of the sequence. For example it can be used for representing the bytes object as a sequence of 1-byte bytes objects (as in 2.x), a generalized alternative to iterbytes() from PEP 467 [2]. Neither itertools nor collections modules look good place for these features, since they are not concrete classes and work only with sequences, not general iterables or iterators. On other side, mappingproxy and ChainMap look close, maybe new module should be oriented not on sequences, but on views. [1] https://pypi.python.org/pypi/dataview [2] https://www.python.org/dev/peps/pep-0467