I'm sure I raised this already but I can't find the issue anywhere, so just for the record:
If you create an XLSX file with Excel, adding a validation list to cell A1, for example, reading this in and then saving it back to disk removes the validation. It seems to be a problem with the reader.
Attached is a simple workbook. To reproduce the problem:
In : import openpyxl In : wb = openpyxl.load_workbook('validation_list.xlsx') In : wb.save('validation_list_out.xlsx')
And see that A1 no longer has validation on it.