Excel Builder

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name: excel-builder description: Build .xlsx files with formulas, merged cells, data validation, conditional formatting, pivot tables, and charts. Use when creating Excel spreadsheets, financial tables, data entry forms, or any structured .xlsx deliverable requiring formulas or formatting. license: MIT metadata: version: "1.0.0" domain: document-generation triggers: Excel, xlsx, spreadsheet, formula, pivot table, chart, data validation, conditional formatting, openpyxl, xlsxwriter, merged cells, workbook role: builder scope: implementation output-format: xlsx related-skills: financial-model-builder, data-analysis-report, pdf-report-generator

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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)

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)

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.