Excel (XLSX) Skill

Overview

This skill provides comprehensive capabilities for working with Excel spreadsheets programmatically using Python. It covers everything from basic file operations to advanced data analysis, formula management, chart creation, and formatting.

The primary library is openpyxl for full Excel file manipulation, supplemented by pandas for data analysis tasks.

Core Capabilities

1. File Operations

• Reading: Load .xlsx, .xlsm, and .csv files
• Writing: Create new Excel workbooks from scratch
• Editing: Modify existing workbooks while preserving formulas, formatting, and charts
• Converting: Transform between CSV, Excel, and other formats

2. Data Management

• Cell Operations: Read, write, and modify individual cells or ranges
• Formulas: Create and manage Excel formulas (SUM, VLOOKUP, INDEX/MATCH, etc.)
• Data Validation: Set dropdown lists, numeric ranges, date constraints
• Named Ranges: Define and use named cell ranges for easier formula management

3. Formatting

• Cell Styling: Fonts, colors, borders, alignment, number formats
• Conditional Formatting: Apply rules-based formatting
• Row/Column Sizing: Set widths, heights, auto-fit
• Merge Cells: Combine cells for headers and labels

4. Charts & Visualizations

• Chart Types: Line, bar, column, pie, scatter, area, combo charts
• Chart Customization: Titles, legends, data labels, colors
• Multiple Series: Multi-dataset charts with secondary axes
• Chart Positioning: Place charts in specific locations

5. Multi-Worksheet Operations

• Sheet Management: Create, rename, delete, reorder worksheets
• Cross-Sheet Formulas: Reference data across multiple sheets
• Sheet Copying: Duplicate sheets with formatting intact
• Sheet Protection: Lock/unlock sheets and ranges

6. Data Analysis

• Filtering: Auto-filter data ranges
• Sorting: Multi-level sorting
• Pivot Tables: Programmatic pivot table creation
• Statistical Functions: Built-in and custom calculations

Installation

# Primary library
pip install openpyxl

# For data analysis
pip install pandas openpyxl

# Or with uv
uv pip install openpyxl pandas

Essential Workflows

Workflow 1: Creating a New Workbook from Scratch

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

# Create new workbook
wb = Workbook()
ws = wb.active
ws.title = "Sales Report"

# Add headers with formatting
headers = ["Product", "Q1", "Q2", "Q3", "Q4", "Total"]
header_fill = PatternFill(start_color="4472C4", end_color="4472C4", fill_type="solid")
header_font = Font(color="FFFFFF", bold=True)

for col, header in enumerate(headers, start=1):
    cell = ws.cell(row=1, column=col, value=header)
    cell.fill = header_fill
    cell.font = header_font
    cell.alignment = Alignment(horizontal="center")

# Add data
data = [
    ["Product A", 1000, 1200, 1100, 1300],
    ["Product B", 800, 900, 950, 1000],
    ["Product C", 1500, 1400, 1600, 1700]
]

for row_idx, row_data in enumerate(data, start=2):
    for col_idx, value in enumerate(row_data, start=1):
        ws.cell(row=row_idx, column=col_idx, value=value)

# Add formulas for totals
for row in range(2, len(data) + 2):
    formula = f"=SUM(B{row}:E{row})"
    ws.cell(row=row, column=6, value=formula)

# Adjust column widths
for col in range(1, 7):
    ws.column_dimensions[get_column_letter(col)].width = 12

# Save workbook
wb.save("sales_report.xlsx")

Workflow 2: Reading and Analyzing Existing Workbooks

from openpyxl import load_workbook

# Load existing workbook
wb = load_workbook('data.xlsx', data_only=True)  # data_only=True evaluates formulas
ws = wb.active

# Method 1: Iterate through all rows
for row in ws.iter_rows(min_row=2, values_only=True):
    print(row)

# Method 2: Read specific cells
value = ws['A1'].value
value = ws.cell(row=2, column=2).value

# Method 3: Read range
for row in ws['B2':'D5']:
    for cell in row:
        print(cell.value, end=' ')
    print()

# Calculate statistics
values = [cell.value for cell in ws['B'][1:] if isinstance(cell.value, (int, float))]
if values:
    print(f"Sum: {sum(values)}")
    print(f"Average: {sum(values) / len(values):.2f}")

wb.close()

Workflow 3: Editing Workbooks While Preserving Formulas

from openpyxl import load_workbook
from openpyxl.styles import Font

# Load workbook WITHOUT data_only to preserve formulas
wb = load_workbook('existing_report.xlsx')
ws = wb['Sales']

# Update values (formulas will recalculate when opened in Excel)
ws['B2'] = 1500
ws['C2'] = 1650

# Add new row with data and formulas
new_row = ws.max_row + 1
ws[f'A{new_row}'] = "Product D"
ws[f'B{new_row}'] = 900
ws[f'C{new_row}'] = 1000
ws[f'D{new_row}'] = 1100
ws[f'E{new_row}'] = 1200
ws[f'F{new_row}'] = f"=SUM(B{new_row}:E{new_row})"  # Add formula

# Apply formatting to new row
for col in range(1, 7):
    cell = ws.cell(row=new_row, column=col)
    if col == 1:
        cell.font = Font(bold=True)

# Save changes
wb.save('existing_report.xlsx')

Workflow 4: Working with Pandas for Data Analysis

import pandas as pd
from openpyxl import load_workbook
from openpyxl.styles import Font, PatternFill

# Step 1: Read and analyze data with pandas
df = pd.read_excel('sales_data.xlsx')

# Perform analysis
summary = df.groupby('Product').agg({
    'Sales': ['sum', 'mean', 'count'],
    'Profit': 'sum'
}).round(2)

summary.columns = ['Total Sales', 'Avg Sales', 'Transactions', 'Total Profit']

# Step 2: Write results to new Excel file
with pd.ExcelWriter('sales_analysis.xlsx', engine='openpyxl') as writer:
    df.to_excel(writer, sheet_name='Raw Data', index=False)
    summary.to_excel(writer, sheet_name='Summary')

# Step 3: Enhance with openpyxl formatting
wb = load_workbook('sales_analysis.xlsx')
ws = wb['Summary']

header_fill = PatternFill(start_color="366092", end_color="366092", fill_type="solid")
header_font = Font(color="FFFFFF", bold=True)

for cell in ws[1]:
    cell.fill = header_fill
    cell.font = header_font

wb.save('sales_analysis.xlsx')

Key Principles

Formula Management

• Always use formulas for calculations instead of hardcoded values
• Formulas update automatically when source data changes
• Use named ranges for complex formulas to improve readability
• Don't use data_only=True when loading files if you need to preserve formulas

Performance Optimization

• For large datasets: Write rows in bulk using ws.append()
• For reading large files: Use read_only=True mode
• For writing large files: Use write_only=True mode
• Avoid cell-by-cell operations in nested loops

Memory Management

• Close workbooks after use: wb.close()
• Use read_only/write_only modes for large files
• Process data in chunks for very large datasets

Error Handling

• Always use try/except blocks for file operations
• Check for empty cells before processing
• Validate data types before calculations
• Handle InvalidFileException for corrupted files

Date and Time

• Use datetime objects for dates, not strings
• Apply proper number formats: cell.number_format = 'mm/dd/yyyy'
• Excel stores dates as numbers internally

Quick Reference

Basic Operations

from openpyxl import Workbook, load_workbook

# Create workbook
wb = Workbook()
ws = wb.active

# Read cell
value = ws['A1'].value
value = ws.cell(row=1, column=1).value

# Write cell
ws['A1'] = "Hello"
ws.cell(row=1, column=1, value="Hello")

# Write formula
ws['C1'] = "=A1+B1"

# Add row
ws.append([1, 2, 3])

# Save and close
wb.save('output.xlsx')
wb.close()

Common Imports

from openpyxl import Workbook, load_workbook
from openpyxl.styles import Font, PatternFill, Border, Side, Alignment
from openpyxl.chart import LineChart, BarChart, PieChart, Reference
from openpyxl.utils import get_column_letter
from openpyxl.data_validation import DataValidation
from openpyxl.formatting.rule import ColorScaleRule, CellIsRule

Common Use Cases

Creating Charts

Add visualizations to your spreadsheets. See examples/workflow-examples.md for complete chart creation workflow including line charts, bar charts, and pie charts.

Conditional Formatting

Apply visual formatting based on cell values. See examples/workflow-examples.md for color scales, icon sets, and rule-based formatting.

Data Validation

Create dropdown lists and input constraints. See examples/workflow-examples.md for dropdown lists, numeric ranges, and date validation.

Multi-Sheet Workbooks

Work with multiple worksheets and cross-sheet formulas. See examples/workflow-examples.md for complete multi-sheet workflow.

Financial Reports

Create professional financial statements. See examples/financial-report.md for a complete income statement example with dynamic formulas.

Data Transformation

Transform CSV data into formatted Excel reports. See examples/data-transformation.md for pandas integration and pivot table creation.

Dashboards

Build executive dashboards with multiple charts. See examples/dashboard-creation.md for comprehensive dashboard with KPIs and visualizations.

Helper Scripts

The scripts/ directory provides utility functions for common operations:

from scripts.excel_helper import (
    create_workbook,
    read_excel_data,
    add_chart,
    apply_formatting,
    add_formula,
    auto_fit_columns
)

# Create new workbook with data
wb, ws = create_workbook("Sales Report", headers=["Product", "Q1", "Q2"])

# Read data from existing file
data = read_excel_data("data.xlsx", sheet_name="Sheet1")

# Add chart to worksheet
add_chart(ws, chart_type="line", data_range="B2:D10", title="Sales Trend")

# Apply formatting
apply_formatting(ws, cell_range="A1:D1", bold=True, bg_color="4472C4")

# Add formula to range
add_formula(ws, cell="E2", formula="=SUM(B2:D2)", copy_down=10)

# Auto-fit all columns
auto_fit_columns(ws)

wb.save("output.xlsx")

Additional Resources

Detailed Documentation

• Library Reference: See references/library-reference.md for complete openpyxl, pandas, and xlsxwriter documentation
• Best Practices: See references/best-practices.md for performance optimization, error handling, and common pitfalls

Complete Examples

• Workflow Examples: examples/workflow-examples.md - Charts, conditional formatting, data validation, multi-sheet operations
• Financial Reports: examples/financial-report.md - Income statement with dynamic formulas
• Data Transformation: examples/data-transformation.md - CSV to Excel with pandas integration
• Dashboard Creation: examples/dashboard-creation.md - Multi-chart dashboard with KPIs

External Links

• openpyxl Documentation: https://openpyxl.readthedocs.io/
• pandas Excel Support: https://pandas.pydata.org/docs/reference/io.html#excel
• Excel Formula Reference: https://support.microsoft.com/en-us/excel

Summary

This skill enables comprehensive Excel automation including:

• Creating complex spreadsheets with formulas and formatting
• Reading and analyzing existing workbooks
• Editing files while preserving formulas and styles
• Creating professional charts and visualizations
• Applying conditional formatting and data validation
• Working with multiple worksheets and cross-sheet formulas
• Integrating with pandas for advanced data analysis
• Handling large datasets efficiently

Use this skill for any task involving Excel files, from simple data entry to complex financial reports and dashboards.