Excel / XLSX

When to Use

Use when the main artifact is a Microsoft Excel workbook or spreadsheet file, especially when formulas, dates, formatting, merged cells, workbook structure, or cross-platform behavior matter.

Core Rules

• Use pandas for analysis, reshaping, and CSV-like tasks.
• Use openpyxl when formulas, styles, sheets, comments, merged cells, or workbook preservation matter.
• Write formulas into cells instead of hardcoding derived results from Python.
• Keep calculations in Excel when the workbook should stay live.
• Preserve workbook structure before changing content.
• Verify no #REF!, #DIV/0!, #VALUE!, #NAME?, or circular-reference fallout remains before delivery.
• Existing templates override generic styling advice.

Common Traps

• Type inference on read can leave numbers as text or convert IDs into damaged numeric values.
• Excel silently truncates numeric precision past 15 digits.
• Saving the wrong workbook view can replace formulas with cached values.
• Hidden sheets, named ranges, validations, and merged areas often keep business logic that is invisible in a quick skim.