Driving Excel from Python in Windows

Question

We have various spreadsheets that employ deliciously complicated macros and third party extensions to produce complicated models. I'm working on a project that involves slightly tweaking various inputs and seeing the results. Rather than doing this by hand or writing VBA, I'd like to see if I can write a python script to drive this. In other words, the python script will start up, load the excel sheet, and then interact with the sheet by making minor changes in some cells and seeing how they affect other cells.

So, my question is twofold:

• What is the best library to use to drive excel from python in such fashion?

• Where's the best documentation/examples on using said library?

Cheers, /YGA

Answer 1

For controlling Excel, use pywin32, like @igowen suggests.

Note that it is possible to use static dispatch. Use makepy.py from the pywin32 project to create a python module with the python wrappers. Using the generated wrappers simplifies development, since for instance ipython gives you tab completion and help during development.

Static dispatch example:

 x:> makepy.py "Microsoft Excel 11.0 Object Library" ... Generating... Importing module x:> ipython 

> from win32com.client import Dispatch > excel = Dispatch("Excel.Application") > wb = excel.Workbooks.Append() > range = wb.Sheets[0].Range("A1") > range.[Press Tab] range.Activate                 range.Merge range.AddComment               range.NavigateArrow range.AdvancedFilter           range.NoteText ... range.GetOffset                range.__repr__ range.GetResize                range.__setattr__ range.GetValue                 range.__str__ range.Get_Default              range.__unicode__ range.GoalSeek                 range._get_good_object_ range.Group                    range._get_good_single_object_ range.Insert                   range._oleobj_ range.InsertIndent             range._prop_map_get_ range.Item                     range._prop_map_put_ range.Justify                  range.coclass_clsid range.ListNames                range.__class__ > range.Value = 32 ... 

Documentation links:

• The O'Reilly book Python Programming on Win32 has an Integrating with Excel chapter.
• Same book, free sample chapter Advanced Python and COM covers makepy in detail.
• Tutorials
• win32com documentation, I suggest you read this first.

Answer 2

I've done this by using pywin32. It's not a particularly pleasant experience, since there's not really any abstraction; it's like using VBA, but with python syntax. You can't rely on docstrings, so you'll want to have the MSDN Excel reference handy (http://msdn.microsoft.com/en-us/library/aa220733.aspx is what I used, if I remember correctly. You should be able to find the Excel 2007 docs if you dig around a bit.).

See here for a simple example.

from win32com.client import Dispatch  xlApp = Dispatch("Excel.Application") xlApp.Visible = 1 xlApp.Workbooks.Add() xlApp.ActiveSheet.Cells(1,1).Value = 'Python Rules!' xlApp.ActiveWorkbook.ActiveSheet.Cells(1,2).Value = 'Python Rules 2!' xlApp.ActiveWorkbook.Close(SaveChanges=0) # see note 1 xlApp.Quit() xlApp.Visible = 0 # see note 2 del xlApp 

Good luck!