Xlsx

The standout feature is mandatory formula recalculation using LibreOffice to catch errors like #REF! and #DIV/0! before you ship. It pushes you toward Excel formulas instead of hardcoding Python calculations, which is the right call if someone else needs to update the spreadsheet later. The guidelines are opinionated about financial modeling conventions (blue for inputs, black for formulas, making zeros display as dashes) but explicitly tell you to ignore them if you're updating an existing template. Works well for building projection models, analyzing datasets, or automating spreadsheet tasks where you need formulas to actually work.