excel-builder

# Excel Builder Builds structured `.xlsx` files programmatically using Python libraries (openpyxl or xlsxwriter). ## When to Use This Skill - Creating Excel spreadsheets with formulas and calculated fields - Building financial tables, budgets, or invoices - Generating data entry forms with validation and dropdowns - Producing reports with charts (bar, line, pie, scatter) - Exporting structured data with conditional formatting or color coding - Building pivot-ready data tables ## Core Workflow 1. **Choose library** — Use `openpyxl` for reading/modifying existing files; use `xlsxwriter` for new write-only files with rich charts 2. **Design structure** — Define sheets, columns, headers, and data rows before writing 3. **Write data** — Populate cells row by row; apply number formats (`"#,##0.00"`, `"YYYY-MM-DD"`) 4. **Add formulas** — Use Excel formula strings: `=SUM(B2:B100)`, `=IF(A2>0, "Yes", "No")` 5. **Format** — Apply styles: bold headers, column widths, merged cells, fill colors, borders 6. **Validate** — Add data validation (dropdown lists, numeric ranges) where applicable 7. **Charts** — Add charts referencing data ranges; set titles and axis labels 8. **Save and verify** — Save to output path; confirm file exists and is non-zero bytes ## Key Patterns ### openpyxl (read/write existing) ```python from openpyxl import Workbook, load_workbook from openpyxl.styles import Font, PatternFill, Alignment wb = Workbook() ws = wb.active ws.title = "Report" ws["A1"] = "Revenue" ws["A1"].font = Font(bold=True, size=12) ws.column_dimensions["A"].width = 20 wb.save("output.xlsx") ``` ### xlsxwriter (new files with charts) ```python import xlsxwriter wb = xlsxwriter.Workbook("output.xlsx") ws = wb.add_worksheet("Summary") bold = wb.add_format({"bold": True, "bg_color": "#4472C4", "font_color": "white"}) ws.write("A1", "Month", bold) chart = wb.add_chart({"type": "column"}) chart.add_series({"values": "=Summary!$B$2:$B$13", "name": "Revenue"}) ws.insert_chart("D2", chart) wb.close() ``` ## Error Handling - If `openpyxl` not installed: `pip install openpyxl` - If `xlsxwriter` not installed: `pip install xlsxwriter` - Always wrap `wb.save()` in try/except; report path conflicts - Verify output with `os.path.getsize(path) > 0` before returning ## Output Return the absolute path to the saved `.xlsx` file. If generating multiple sheets, list each sheet name and row count in a brief summary.