intspan is a set subclass that conveniently stores sets of integers. Sets can be created from and displayed as integer spans such as 1-3,14,29,92-97 rather than exhaustive member listings. Compare:
intspan('1-3,14,29,92-97') [1, 2, 3, 14, 29, 92, 93, 94, 95, 96, 97]
Or worse, the unsorted, non-intuitive listings that crop up with Python's native unordered sets, such as:
set([96, 1, 2, 3, 97, 14, 93, 92, 29, 94, 95])
While they all indicate the same values, intspan is more compact. And it better divulges the contiguous nature of segments of the collection, making it easier for humans to quickly determine the "shape" of the data and ascertain "what's missing?"
When iterating, pop()-ing an item, or converting to a list, intspan behaves as if it were an ordered--in fact, sorted--collection. A key implication is that, regardless of the order in which items are added, an intspan will always be rendered in the most compact, organized form possible.
The main draw is having a convenient way to specify (possibly discontinuous) ranges--for example, rows to process in a spreadsheet. It can also help you quickly identify or report which items were not successfully processed in a large dataset.
There is also an ordered intspanlist type that helps specify the ordering of a set of elements.
For this and more, see the full details on Read the Docs.