MODSetter XLSX
Author the workbook with xlsxwriter, saving to a BytesIO opened with
{"in_memory": True}. XlsxWriter is preferred because it writes the explicit
formula caches the in-browser grid needs.
Authoring rules
- Prefer one clear purpose per worksheet. Name sheets for their content, not
Sheet1/Sheet2. - Set column widths deliberately. Freeze header rows when tables are scrolled.
- Style headers once (bold, fill, borders) and reuse the format objects. Prefer
number formats (
#,##0.00,0%, dates) over pre-formatted strings. - Write formulas with both the formula string and a computed cached value:
worksheet.write_formula("B2", "=A2*1.1", fmt, 110). The grid shows the cache rather than recalculating, so a missing cache renders blank. - Never leave Excel error literals (
#DIV/0!,#REF!,#VALUE!,#N/A) as cached results. Fix the formula or the inputs instead. - Keep workbooks compact — prefer tight tables over giant empty ranges.
- Charts, pivot tables, macros, and VBA are out of scope; stick to values, formulas, formats, panes, and multiple sheets.