Xlsx

1. Choose tool (pandas for data, openpyxl for formulas/formatting)
2. Create/Load workbook
3. Modify data, formulas, formatting
4. Save
5. Recalculate formulas (mandatory): python scripts/recalc.py output.xlsx
6. Verify and fix any errors from recalc output

Creating Excel Files (openpyxl)

from openpyxl import Workbook
from openpyxl.styles import Font, PatternFill, Alignment

wb = Workbook()
sheet = wb.active
sheet['A1'] = 'Revenue'
sheet['B2'] = '=SUM(A1:A10)'
sheet['A1'].font = Font(bold=True)
sheet.column_dimensions['A'].width = 20
wb.save('output.xlsx')

Reading Data (pandas)

import pandas as pd
df = pd.read_excel('file.xlsx')
all_sheets = pd.read_excel('file.xlsx', sheet_name=None)

Financial Model Standards

Color Coding

• Blue text: Hardcoded inputs
• Black text: ALL formulas and calculations
• Green text: Links from other worksheets
• Red text: External links
• Yellow background: Key assumptions needing attention

Number Formatting

• Years as text strings ("2024" not "2,024")
• Currency: $#,##0 with units in headers
• Zeros display as "-"
• Percentages: 0.0%
• Negatives: parentheses (123) not -123

Formula Verification Checklist

• Test 2-3 sample references before building full model
• Confirm column mapping (column 64 = BL, not BK)
• Row offset: DataFrame row 5 = Excel row 6
• Handle NaN with pd.notna()
• Check for #DIV/0!, #REF!, #VALUE! errors after recalc

Attribution

From anthropics/skills xlsx skill (Proprietary — see LICENSE.txt in source repo for terms).