finding dupes (with a twist)

[stullis]

You have the right idea. Python's a general purpose language so it can do pretty much anything a computer is capable of doing. The logic is sound though you'll need at least one try...except block for indexing errors.

If your interest is cleaning out the duplicates, you could use a dictionary of sets to eliminate duplicates and then rebuild the Excel sheet with the clean data. You'd only have to iterate once and sorting would not be required.