How to get OpenPyXL column letter by index

If you want to access OpenPyXL columns using indices instead of letters, use

import openpyxl.utils.cell

openpyxl.utils.cell.get_column_letter(idx)

Note that idx is 1-based: index 0 is not a valid argument & index 1 yields column name A 

For example:

openpyxl.utils.cell.get_column_letter(3) # returns "C"