Excel Automation

daymade/claude-code-skills/daymade-docs/excel-automation

by daymade2c6d263d1fccNo license1.4K starsListed Oct 8, 2026Updated Oct 8, 2026Repository updated today

Create, parse, and control Excel files on macOS. Professional formatting with openpyxl, complex xlsm parsing with stdlib zipfile+xml for investment bank financial models, and Excel window control via AppleScript. Use when creating formatted Excel reports, parsing financial models that openpyxl cannot handle, or automating Excel on macOS.

AI-generated overview

Create formatted Excel files, parse complex xlsm workbooks, and control Excel on macOS.

What it does
This skill produces professionally formatted Excel workbooks with openpyxl, including investment-banking color conventions, number formats and conditional formatting. It also parses complex xlsm/xlsx files that openpyxl cannot handle by reading the underlying ZIP and XML directly, and can repair corrupted defined names. On macOS it drives the Excel application through AppleScript to activate files, set zoom, scroll and select cells.
When to use it
Use it when generating formatted Excel reports, dashboards or mockups, when extracting data from large or macro-enabled financial models that openpyxl fails on, or when automating an Excel window on macOS.
Requirements
Python executed via uv with the openpyxl package for creation; the parsing path uses only the Python standard library (zipfile, xml.etree). macOS with Microsoft Excel and osascript is needed for the window-control features. It ships two executable scripts and a formatting reference document.

Excel Automation

Create professional Excel files, parse complex financial models, and control Excel on macOS.

Quick Start

bash
# Create a formatted Excel reportuv run --with openpyxl scripts/create_formatted_excel.py output.xlsx
# Parse a complex xlsm that openpyxl can't handleuv run scripts/parse_complex_excel.py model.xlsm              # List sheetsuv run scripts/parse_complex_excel.py model.xlsm "DCF"        # Extract a sheetuv run scripts/parse_complex_excel.py model.xlsm --fix        # Fix corrupted names
# Control Excel via AppleScript (with timeout to prevent hangs)timeout 5 osascript -e 'tell application "Microsoft Excel" to activate'

Overview

Three capabilities:

CapabilityToolWhen to Use
Create formatted ExcelopenpyxlReports, mockups, dashboards
Parse complex xlsm/xlsxzipfile + xml.etreeFinancial models, VBA workbooks, >1MB files
Control Excel windowAppleScript (osascript)Zoom, scroll, select cells programmatically

Tool Selection Decision Tree

Is the file simple (data export, no VBA, <1MB)?├─ YES → openpyxl or pandas└─ NO   ├─ Is it .xlsm or from investment bank / >1MB?   │   └─ YES → zipfile + xml.etree.ElementTree (stdlib)   └─ Is it truly .xls (BIFF format)?       └─ YES → xlrd

Signals of "complex" Excel: file >1MB, .xlsm extension, from investment bank/broker, contains VBA macros.

IMPORTANT: Always run file <path> first — extensions lie. A .xls file may actually be a ZIP-based xlsx.

Creating Excel Files (openpyxl)

Professional Color Convention (Investment Banking Standard)

ColorRGB CodeMeaning
Blue0000FFUser input / assumption
Black000000Calculated value
Green008000Cross-sheet reference
White on dark blueFFFFFF on 4472C4Section headers
Dark blue text1F4E79Title

Core Formatting Patterns

python
from openpyxl.styles import Font, PatternFill, Border, Side, Alignment
# FontsBLUE_FONT = Font(color="0000FF", size=10, name="Calibri")BLACK_FONT_BOLD = Font(color="000000", size=10, name="Calibri", bold=True)GREEN_FONT = Font(color="008000", size=10, name="Calibri")HEADER_FONT = Font(color="FFFFFF", size=12, name="Calibri", bold=True)
# FillsDARK_BLUE_FILL = PatternFill("solid", fgColor="4472C4")LIGHT_BLUE_FILL = PatternFill("solid", fgColor="D9E1F2")INPUT_GREEN_FILL = PatternFill("solid", fgColor="E2EFDA")LIGHT_GRAY_FILL = PatternFill("solid", fgColor="F2F2F2")
# BordersTHIN_BORDER = Border(bottom=Side(style="thin", color="B2B2B2"))BOTTOM_DOUBLE = Border(bottom=Side(style="double", color="000000"))

Number Format Codes

FormatCodeExample
Currency'$#,##0'$1,234
Currency with decimals'$#,##0.00'$1,234.56
Percentage'0.0%'12.3%
Percentage (2 decimal)'0.00%'12.34%
Number with commas'#,##0'1,234
Multiplier'0.0x'1.5x

Conditional Formatting (Sensitivity Tables)

Red-to-green gradient for sensitivity analysis:

python
from openpyxl.formatting.rule import ColorScaleRule
rule = ColorScaleRule(    start_type="min", start_color="F8696B",   # Red (low)    mid_type="percentile", mid_value=50, mid_color="FFEB84",  # Yellow (mid)    end_type="max", end_color="63BE7B"         # Green (high))ws.conditional_formatting.add(f"B2:F6", rule)

Execution

bash
uv run --with openpyxl scripts/create_formatted_excel.py

Full template script: See scripts/create_formatted_excel.py

Parsing Complex Excel (zipfile + xml)

When openpyxl fails on complex xlsm files (corrupted DefinedNames, complex VBA), use stdlib directly.

XLSX Internal ZIP Structure

file.xlsx (ZIP archive)├── [Content_Types].xml├── xl/│   ├── workbook.xml          ← Sheet names + order│   ├── sharedStrings.xml     ← All text values (lookup table)│   ├── worksheets/│   │   ├── sheet1.xml        ← Cell data for sheet 1│   │   ├── sheet2.xml        ← Cell data for sheet 2│   │   └── ...│   └── _rels/│       └── workbook.xml.rels ← Maps rId → sheetN.xml└── _rels/.rels

Sheet Name Resolution (Two-Step)

Sheet names in workbook.xml link to physical files via _rels/workbook.xml.rels:

python
import zipfileimport xml.etree.ElementTree as ET
MAIN_NS = 'http://schemas.openxmlformats.org/spreadsheetml/2006/main'REL_NS = 'http://schemas.openxmlformats.org/officeDocument/2006/relationships'RELS_NS = 'http://schemas.openxmlformats.org/package/2006/relationships'
def get_sheet_path(zf, sheet_name):    """Resolve sheet name to physical XML file path inside ZIP."""    # Step 1: workbook.xml → find rId for the sheet name    wb_xml = ET.fromstring(zf.read('xl/workbook.xml'))    sheets = wb_xml.findall(f'.//{{{MAIN_NS}}}sheet')    rid = None    for s in sheets:        if s.get('name') == sheet_name:            rid = s.get(f'{{{REL_NS}}}id')            break    if not rid:        raise ValueError(f"Sheet '{sheet_name}' not found")
    # Step 2: workbook.xml.rels → map rId to file path    rels_xml = ET.fromstring(zf.read('xl/_rels/workbook.xml.rels'))    for rel in rels_xml.findall(f'{{{RELS_NS}}}Relationship'):        if rel.get('Id') == rid:            return 'xl/' + rel.get('Target')
    raise ValueError(f"No file mapping for {rid}")

Cell Data Extraction

python
def extract_cells(zf, sheet_path):    """Extract all cell values from a sheet XML."""    # Build shared strings lookup    shared = []    try:        ss_xml = ET.fromstring(zf.read('xl/sharedStrings.xml'))        for si in ss_xml.findall(f'{{{MAIN_NS}}}si'):            texts = si.itertext()            shared.append(''.join(texts))    except KeyError:        pass  # No shared strings
    # Parse sheet cells    sheet_xml = ET.fromstring(zf.read(sheet_path))    rows = sheet_xml.findall(f'.//{{{MAIN_NS}}}row')
    data = {}    for row in rows:        for cell in row.findall(f'{{{MAIN_NS}}}c'):            ref = cell.get('r')         # e.g., "A1"            cell_type = cell.get('t')   # "s" = shared string, None = number            val_el = cell.find(f'{{{MAIN_NS}}}v')
            if val_el is not None and val_el.text:                if cell_type == 's':                    data[ref] = shared[int(val_el.text)]                else:                    try:                        data[ref] = float(val_el.text)                    except ValueError:                        data[ref] = val_el.text    return data

Fixing Corrupted DefinedNames

Investment bank xlsm files often have corrupted <definedName> entries containing "Formula removed":

python
def fix_defined_names(zf_in_path, zf_out_path):    """Remove corrupted DefinedNames and repackage."""    import shutil, tempfile    with tempfile.TemporaryDirectory() as tmp:        tmp = Path(tmp)        with zipfile.ZipFile(zf_in_path, 'r') as zf:            zf.extractall(tmp)
        wb_xml_path = tmp / 'xl' / 'workbook.xml'        tree = ET.parse(wb_xml_path)        root = tree.getroot()
        ns = {'main': MAIN_NS}        defined_names = root.find('.//main:definedNames', ns)        if defined_names is not None:            for name in list(defined_names):                if name.text and "Formula removed" in name.text:                    defined_names.remove(name)
        tree.write(wb_xml_path, encoding='utf-8', xml_declaration=True)
        with zipfile.ZipFile(zf_out_path, 'w', zipfile.ZIP_DEFLATED) as zf:            for fp in tmp.rglob('*'):                if fp.is_file():                    zf.write(fp, fp.relative_to(tmp))

Full template script: See scripts/parse_complex_excel.py

Controlling Excel on macOS (AppleScript)

All commands verified on macOS with Microsoft Excel.

Verified Commands

bash
# Activate Excel (bring to front)osascript -e 'tell application "Microsoft Excel" to activate'
# Open a fileosascript -e 'tell application "Microsoft Excel" to open POSIX file "/path/to/file.xlsx"'
# Set zoom level (percentage)osascript -e 'tell application "Microsoft Excel"    set zoom of active window to 120end tell'
# Scroll to specific rowosascript -e 'tell application "Microsoft Excel"    set scroll row of active window to 45end tell'
# Scroll to specific columnosascript -e 'tell application "Microsoft Excel"    set scroll column of active window to 3end tell'
# Select a cell rangeosascript -e 'tell application "Microsoft Excel"    select range "A1" of active sheetend tell'
# Select a specific sheet by nameosascript -e 'tell application "Microsoft Excel"    activate object sheet "DCF" of active workbookend tell'

Timing and Timeout

Always add sleep 1 between AppleScript commands and subsequent operations (e.g., screenshot) to allow UI rendering.

IMPORTANT: osascript will hang indefinitely if Excel is not running or not responding. Always wrap with timeout:

bash
# Safe pattern: 5-second timeouttimeout 5 osascript -e 'tell application "Microsoft Excel" to activate'
# Check exit code: 124 = timed outif [ $? -eq 124 ]; then    echo "Excel not responding — is it running?"fi

Common Mistakes

MistakeCorrection
openpyxl fails on complex xlsm → try monkey-patchingSwitch to zipfile + xml.etree immediately
Count Chinese characters with wc -cUse wc -m (chars, not bytes; Chinese = 3 bytes/char)
Trust file extensionRun file <path> first to confirm actual format
openpyxl load_workbook hangs on large xlsmUse zipfile for targeted extraction instead of loading entire workbook

Important Notes

  • Execute Python scripts with uv run --with openpyxl (never use system Python)
  • LibreOffice (soffice --headless) can convert formats and recalculate formulas
  • Detailed formatting reference: See references/formatting-reference.md

Source and attribution

Source:daymade/claude-code-skillsindaymade-docs/excel-automationat commit2c6d263

License: No license

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