I’m working on a regression-testing tool that will validate a very large number of Excel spreadsheets. At the moment I control them via COM from a Python script using the latest version of the pywin32 product. Unfortunately COM seems to have a number of annoying drawbacks:
For example, the slightest upset seems to be able to break the connection to the COM-Server, once severed there seems to be no safe way to re-connect to the Excel application. There’s absolutely no safety built into the COM Application object.
The Excel COM interface will not allow me to safely remote-control two seperate instances of the Excel application operating on the same workbook file, even if they are read-only.
Also when something does go wrong I seldom get any useful error-messages… at best I can except a numerical error-code or a barely useful message such as ‘An Exception has occurred’. It’s almost impossible to know why something went wrong.
Finally, COM lacks the ability to control some of the most fundamental aspects of Excel? For example there’s no way to do a guaranteed close of just the Excel process that a COM client is connected to. You cannot even use COM to find Excel’s PID.
So what if I were to completely abandon COM? Is there an alternative way to control Excel?
All I want to do is run macros, open and close workbooks and read and write cell-ranges? Perhaps some .NET experts know a trick or two which have not yet bubbled into the Python community? What about you office-hackers? Could there be a better way to get at Excel’s innards than COM?
There is no way that completely bypasses COM. You can use VSTO (Visual Studio Tools for Office), which has nice .NET wrappers on the COM objects, but it is still COM underneath.