python-win32com excel com model started generating errors

Over the last few days, I have been working on automating the generation of some pivot tables for a number of reports.

Boiled down to the minimum, the following code was working without issue:

import win32com.client    
objExcelApp = win32com.client.gencache.EnsureDispatch('Excel.Application')
objExcelApp.Visible = 1

This would pop-up an instance of excel and I could continue working in Python. But suddenly, today my scripts are failing with the following:

>>>import win32com.client
>>> objExcelApp = win32com.client.gencache.EnsureDispatch('Excel.Application')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:Program Files (x86)Python37-32libsite-packageswin32comclientgencache.py", line 534, in EnsureDispatch
    mod = EnsureModule(tla[0], tla[1], tla[3], tla[4], bForDemand=bForDemand)
  File "C:Program Files (x86)Python37-32libsite-packageswin32comclientgencache.py", line 391, in EnsureModule
    module = GetModuleForTypelib(typelibCLSID, lcid, major, minor)
  File "C:Program Files (x86)Python37-32libsite-packageswin32comclientgencache.py", line 266, in GetModuleForTypelib
    AddModuleToCache(typelibCLSID, lcid, major, minor)
  File "C:Program Files (x86)Python37-32libsite-packageswin32comclientgencache.py", line 552, in AddModuleToCache
    dict = mod.CLSIDToClassMap
AttributeError: module 'win32com.gen_py.00020813-0000-0000-C000-000000000046x0x1x9' has no attribute 'CLSIDToClassMap'

The code has not changed from yesterday to today. I have no idea what is happening!!!.

Another interesting kicker. if I do the same code in the same session again I get a different error:

>>> objExcelApp = win32com.client.gencache.EnsureDispatch('Excel.Application')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:Program Files (x86)Python37-32libsite-packageswin32comclientgencache.py", line 534, in EnsureDispatch
    mod = EnsureModule(tla[0], tla[1], tla[3], tla[4], bForDemand=bForDemand)
  File "C:Program Files (x86)Python37-32libsite-packageswin32comclientgencache.py", line 447, in EnsureModule
    if module.MinorVersion != tlbAttributes[4] or genpy.makepy_version != module.makepy_version:
AttributeError: module 'win32com.gen_py.00020813-0000-0000-C000-000000000046x0x1x9' has no attribute 'MinorVersion'
>>>

So I jump over to a windows machine with a fresh windows install, install python37 and pip install pypiwin32. Run the very same lines and excel opens just like it did yesterday on my original machine.

I tried un-installing and re-installing with no luck. Any idea what is going on here?

NOTE: Dynamic dispatch still works:

import win32com.client
objExcelApp = win32com.client.Dispatch("Excel.Application")
objExcelApp.Visible = 1

But I specifically need static dispatch as Pivot Tables won’t work with a dynamically dispatched object (much later in my code):

objExcelPivotCache = objExcelWorkbook.PivotCaches().Create(SourceType=win32c.xlDatabase, SourceData=objExcelPivotSourceRange)

Answer

I had the same issue and I resolved it by following the instructions here: https://mail.python.org/pipermail/python-win32/2007-August/006147.html

Deleting the gen_py output directory and re-running makepy SUCCEEDS and subsequently the test application runs OK again.

So the symptom is resolved, but any clues as to how this could have happened. This is a VERY long running application (think 24×7 for years) and I’m concerned that whatever caused this might occur again.

To find the output directory, run this in your python console / python session:

import win32com
print(win32com.__gen_path__)

Based on the exception message in your post, the directory you need to remove will be titled ‘00020813-0000-0000-C000-000000000046x0x1x9’. So delete this directory and re-run the code. And if you’re nervous about deleting it (like I was) just cut the directory and paste it somewhere else.

💡Note that this directory is usually in your “TEMP” directory (copy-paste %TEMP%/gen_py in Windows File Explorer and you will arrive there directly).

I have no idea why this happens nor do I know how to prevent it from happening again, but the directions in the link I provided seemed to work for me.