Not sure if this is a user error, a bug or a feature request.
I am using the latest released package.
The following code corrupted my workbook. The problem was that the column letters were in lower case.
decimal = DataValidation(type="decimal") decimal.ranges.append("c2:e14") ws.add(decimal) ... Save the workbook
Next time i loaded the workbook using openpyxl, an exception was raised after the regex which expects upper-case range letters failed.
So if this is not a user error, i suggest that openpyxl will either fail when entering a range which does not match the regex or use a more robust regex allowing lower-case column letters.