# XLSX

> Use this skill any time a spreadsheet file is the primary input or output. This means any task where the user wants to: open, read, edit, or fix an existing .xlsx, .xlsm, .csv, or .tsv file; create a new spreadsheet from scratch or from other data sources; or convert between tabular file formats.

- Skill: `edorabma9304/xlsx` (Agent Skill)
- Install (CLI): `npx skillmds@latest add edorabma9304/xlsx`
- Raw SKILL.md: https://api.skillmd.com/api/skills/edorabma9304/xlsx/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Data & Analytics
- Author: edorabma9304 (https://skillmd.com/u/edorabma9304)
- Updated: 2026-09-22
- Page: https://skillmd.com/skills/edorabma9304/xlsx

---


# Excel / Spreadsheet Skill

## Professional Standards
- Consistent, professional font (Arial, Times New Roman)
- Zero formula errors (#REF!, #DIV/0!, #VALUE!, #N/A, #NAME?)
- Preserve existing template formats when updating files

## Financial Model Color Coding
- **Blue text**: Hardcoded inputs
- **Black text**: Formulas and calculations
- **Green text**: Internal worksheet links
- **Red text**: External file links
- **Yellow background**: Key assumptions

## Number Formatting
- Years as text ("2024")
- Currency with units in headers ("Revenue ($mm)")
- Zeros displayed as "-"
- Percentages at 0.0%
- Negative numbers in parentheses (123)

## CRITICAL: Use Formulas, Not Hardcoded Values

Always use Excel formulas instead of calculating values and hardcoding them.

### WRONG
```python
total = df['Sales'].sum()
sheet['B10'] = total  # Hardcodes 5000
```

### CORRECT
```python
sheet['B10'] = '=SUM(B2:B9)'
```

## Tool Selection

### pandas — Data analysis and bulk operations
```python
import pandas as pd
df = pd.read_excel('file.xlsx')
df.to_excel('output.xlsx', index=False)
```

### openpyxl — Complex formatting and formulas
```python
from openpyxl import Workbook
from openpyxl.styles import Font, PatternFill, Alignment

wb = Workbook()
sheet = wb.active
sheet['A1'] = 'Hello'
sheet['B2'] = '=SUM(A1:A10)'
sheet['A1'].font = Font(bold=True, color='FF0000')
sheet.column_dimensions['A'].width = 20
wb.save('output.xlsx')
```

### SheetJS (JavaScript — used in this project)
```javascript
import * as XLSX from 'xlsx'

// Export data to Excel
const ws = XLSX.utils.json_to_sheet(data)
const wb = XLSX.utils.book_new()
XLSX.utils.book_append_sheet(wb, ws, 'Laporan')
XLSX.writeFile(wb, 'laporan.xlsx')

// Read Excel
const workbook = XLSX.read(buffer, { type: 'buffer' })
const sheet = workbook.Sheets[workbook.SheetNames[0]]
const jsonData = XLSX.utils.sheet_to_json(sheet)
```

## Editing Existing Files
```python
from openpyxl import load_workbook

wb = load_workbook('existing.xlsx')
sheet = wb.active
sheet['A1'] = 'New Value'
sheet.insert_rows(2)
wb.save('modified.xlsx')
```

## Best Practices
- Cell indices are 1-based in openpyxl
- Use `data_only=True` to read calculated values
- Warning: `data_only=True` + save = formulas permanently lost
- For large files: `read_only=True` or `write_only=True`
- Always verify formulas with edge cases (zero, negative values)
- Document data sources for hardcoded values