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python – COM: excelApplication.Application.Quit() preserves the process

Posted by: admin March 9, 2020 Leave a comment

Questions:

I’m using COM integration to drive MS Excel from Python 2.7. I noticed a peculiar thing: when I run the following bit of code:

import win32com.client
excelApp = win32com.client.dynamic.Dispatch('Excel.Application')

an EXCEL.EXE process appears on the processes list (which view using the Windows Task Manager or subprocess.Popen('tasklist')) as expected. I then do all the stuff I need to do no problem. However, when I close Excel:

excelApp.Application.Quit()

The process persists, even if I close the Python interpreter which started it (this kind of makes sense as Excel runs in a different process but just to be sure). The only way I’ve found to terminate this process is either by hand, using the Task Manager, or by calling:

subprocess.Popen("taskkill /F /im EXCEL.EXE",shell=True)

the forceful /F flag is necessary, otherwise the process doesn’t terminate.

This isn’t really a problem (I hope) but I wanted to ask whether this could cause issues when I first edit the documents “normally”, then when calling Excel from python and then “normally” again? Potentially many (couple dozens) times in a row? What I’m worried about is creating conflicting versions of documents etc. Or should I just terminate the EXCEL.EXE process each time just to be safe?

Also I noticed that subprocess.Popen("taskkill") doesn’t return any exceptions that I can catch and anylse (or am I doing something worng here?). I’m particularly interested in distinguishing between the “non-existent process” kill attempt and a failed attempt to terminate the process.

How to&Answers:

try closing any open books, telling the app to quit and delete any references to the app. I usually wrap my com objects in a class. This is what my quit method looks like.

      def quit(self):
        self.xlBook.Close(SaveChanges=0)
        self.xlApp.Quit()
        del self.xlApp

Are you calling Dispatch from the main thread? If not be sure to call

pythoncom.CoInitialize()

before Dispatch, and

pythoncom.CoUninitialize()

after Quit