How to add “Microsoft Excel Object” VBA code to Excel file using Python

Question

I have a long script written in VBA, in Excel. I'm using Python to create another Excel file, and I want to embed the script in that file. I have been able to add a macro as "Module1" in Excel, but not as a "Microsoft Excel Object" associated with a specific worksheet. It has to be associated with one named worksheet, because it highlights particular cells when you click on input cells.

I've extracted the vbaProject.bin into the same folder as the Excel file I want to add it to. I have also remembered to set the correct permissions in Excel (File -> Options -> Trust Center -> Trust Center Settings -> Macro Settings -> Trust Access to the VBA Project Object Model).

I've just generated a file called output.xlsm that opens without issue, contains no VBA, and has multiple worksheets, before starting this code.

I hope this is clear - I am a newbie and this is my first question.

import os
import win32com.client

mydir = os.getcwd()

with open ('vbaProject.bin', 'rb') as myfile:
    print('Reading macro into string from vbaProject.bin')
    macro = myfile.read()

excel = win32com.client.Dispatch('Excel.Application')
excel.Visible = False
workbook = excel.Workbooks.Open(Filename = mydir + '/output.xlsm')
excelModule = workbook.VBProject.VBComponents.Add(1)
excelModule.CodeModule.AddFromString(macro)
excel.Workbooks(1).Close(SaveChanges = 1)
excel.Application.Quit()
del excel

This code adds "Module1" rather than a Microsoft Excel Object.

Also, when I try to close the new Excel file, the macro that I've added as "Module1" has not formed properly. It's a few gobbledegook characters, instead of a long script.

Thanks for any help you can offer.

Answer 1

If you want to add code to a specific, already existing sheet you need to use that sheet's CodeName as an index of the VBComponents collection.

excelModule = workbook.VBProject.VBComponents("SheetCodeName_NotSheetName")
excelModule.CodeModule.AddFromString(macro)

You could also .AddFromFile("path/to/file/filename") or .CreateEventProc("EventName", "ObjectName") .
The latter returns a Long indicating the start of the EventProcedure where you can

excelModule.CodeModule.InsertLines(LineNumberWhereToInsert, "Your code as String")

However you choose to insert the code make sure it's formatted correctly. VBA uses 4 spaces for a tab, CR + LF combination on Windows and CR on Mac for new lines. And be extra careful with special characters.