Excel COM API Reference Skill

This skill provides an API reference for Microsoft Excel COM objects accessed via pywin32. It is primarily intended for use with the PyXLL Excel add-in, but applies equally to any Python code that drives Excel via COM.

Prerequisite: PyXLL Code

BEFORE writing any code that uses a PyXLL decorator, function, or config key (@xl_func, @xl_menu, @xl_macro, xl_app, pyxll.cfg, etc.) — invoke the fetch-pyxll-docs skill using the Skill tool. Do this before writing any code. PyXLL APIs are not covered by this skill; the live docs are the only authoritative source.

Rules for AI Agents

These rules are mandatory. Follow them before writing any Excel COM code.

1. Always read the relevant reference file before using any Excel COM class. Do not rely on training-data knowledge of the Excel COM API — method signatures, parameter names, and property types must be verified from the resources/ docs. The API is large and easy to misremember.

2. Before using any class, look it up in resources/index.md to find which file covers it, then read its section in that file. At minimum, check: which members are properties vs methods vs property accessors, and what the parameter names and types are.

3. Never guess a method or property name. If you cannot find a member in the docs, say so rather than inventing one. COM errors from wrong names surface only at runtime.

4. Property accessors (GetX / SetX) must be called as methods, not accessed as attributes. They appear under "Property Accessors" in the docs. Example: rng.GetOffset(1, 0) — NOT rng.Offset.

5. Always use win32com.client.constants.<name> for enum/constant values. Never use bare integer literals for constants. The constant name (e.g. xlCenter) is the authoritative identifier; its integer value can change across Excel versions. The integer values in resources/enums_xl.md are for reference only — use the named constant, not the number.

6. Use pyxll.xl_app() to get the Application object when running inside Excel via PyXLL. Only use win32com.client.Dispatch("Excel.Application") in external scripts.

7. Parameters marked ? are optional. Required parameters have no ? suffix. Do not omit required parameters.

8. Always check resources/index.md to locate any class — it lists every class and the file that documents it.

9. When operating on cells by category (blanks, formulas, constants, errors, etc.), use SpecialCells(Type) to select them rather than reading the full range value and filtering in Python. Example: rng.SpecialCells(c.xlCellTypeBlanks) selects all blank cells in one call. Python iteration over range values is slower and bypasses the COM object model.

Getting the Application Object

With PyXLL (running inside Excel): use pyxll.xl_app() to get the Application object for the current running Excel instance:

from pyxll import xl_app
import win32com.client

app = xl_app()          # returns the live Excel Application
c = win32com.client.constants

Without PyXLL (external script): use win32com.client.Dispatch:

import win32com.client

app = win32com.client.Dispatch("Excel.Application")
c = win32com.client.constants

Do not use win32com.client.gencache.EnsureDispatch — use Dispatch only.

Everything below app in the object hierarchy is identical in both cases.

API Reference Files

The resources/ directory contains machine-readable reference docs:

Key Conventions

• Properties — accessed as attributes: ws.Name, rng.Value, rng.Font.Bold
• Methods — called normally: rng.Clear(), ws.Copy(), app.Calculate()
• Property Accessors — parameterized properties that must be called as methods: rng.GetOffset(1, 0), rng.GetAddress(False, False), rng.GetResize(3, 2)
• Optional params — marked with ? in the reference: Find(What, After?, LookIn?...)
• Any type — means the COM type wasn't resolved; usually str, int, bool, or float
• Constants — use win32com.client.constants.<name> at runtime, e.g. win32com.client.constants.xlOpenXMLWorkbook. Integer values are listed in resources/enums_xl.md.

Object Hierarchy

Application
  ├─ Workbooks -> Workbook
  │    ├─ Worksheets -> Worksheet
  │    │    ├─ Range  (also .Cells, .Rows, .Columns)
  │    │    │    ├─ .Font, .Interior, .Borders
  │    │    │    ├─ .FormatConditions
  │    │    │    └─ .Hyperlinks, .Comment, .Validation
  │    │    ├─ Shapes -> Shape
  │    │    ├─ ListObjects -> ListObject
  │    │    ├─ PageSetup
  │    │    └─ AutoFilter
  │    ├─ Charts -> Chart
  │    │    ├─ Axes -> Axis, SeriesCollection -> Series
  │    │    └─ ChartArea, PlotArea, Legend
  │    ├─ Names (named ranges)
  │    └─ PivotCaches -> PivotCache
  └─ Windows -> Window -> Panes -> Pane

Common Patterns

from pyxll import xl_app          # PyXLL: use xl_app() inside Excel
import win32com.client

app = xl_app()                     # or: win32com.client.Dispatch("Excel.Application")
c = win32com.client.constants

wb = app.ActiveWorkbook            # or: app.Workbooks.Open(r"C:\path\to\file.xlsx")
ws = wb.Worksheets("Sheet1")

# Read/write cells
rng = ws.Range("A1:B10")
rng.Value = [[1, 2], [3, 4]]

# Formatting
rng.Font.Bold = True
rng.Interior.Color = 0xFFFF00     # yellow
rng.Borders.LineStyle = c.xlContinuous

# Enum constants via win32com.client.constants
wb.SaveAs(r"C:\out.xlsx", FileFormat=c.xlOpenXMLWorkbook)
ws.Cells.HorizontalAlignment = c.xlCenter