I've been looking for ages to find a suitable module to interact with excel, which needs to do the following:

Check a column of cells for an "incorrect" value and change it
Check for empty cells, and if so, replace it
Check a cell value is consistent with the contents of another cell(for example, if called Datasheet, the code in another cell = DS)and if not, change it.

I've looked at openpxyl but I am running Python 3 and I can only seem to find it working for 2. 
I've seen a few others but they seem to be mainly focusing creating a new spreadsheet and simple writing/reading.
The Pandas library is amazing to work with excel files. It can read excel files easily and you then have access to a lot of tools. You can do all the operations you mentionned above. You can also save your result in the excel format
Python 3 and Excel, Finding complex module to use