How can I force python(using win32com) to create a new instance of excel?

Question

I'm automating some excel related tasks which take a long time.

I'm creating an excel instance using:

excel = win32.gencache.EnsureDispatch('Excel.Application')
wb = excel.Workbooks.Add()

however, after the script starts running, if i select an open excel workbook(not the one python is working on), The python script crashes. However, if I open a new excel workbook and type stuff into it, the python script is unaffected.

Is there a particular way I can call excel to prevent this from happening? Or any other solution?

EDIT: This seems to work.

excel = win32.DispatchEx('Excel.Application')

It wouldn't hurt if you would also mention what versions are you using just in case. — Cristian Ciupitu
– Cristian Ciupitu, Commented Mar 15, 2011 at 10:30
well whats the situation with the question? Did you find an answer? Please let us know. — Arnab Ghosal
– Arnab Ghosal, Commented Jan 11, 2012 at 16:18
@jck You should post this as answer instead of editing it in the question — Tobias Kienzler
– Tobias Kienzler, Commented Feb 15, 2017 at 12:46

Winand · Accepted Answer · 2021-02-26 05:05:28Z

Here's a way to create a new instance and use static cache (which is faster and gives an ability to use kwargs):

import sys
import shutil
import pythoncom
from win32com.client import gencache

def EnsureDispatchEx(clsid, new_instance=True):
    """Create a new COM instance and ensure cache is built,
       unset read-only gencache flag"""
    if new_instance:
        clsid = pythoncom.CoCreateInstanceEx(clsid, None, pythoncom.CLSCTX_SERVER,
                                             None, (pythoncom.IID_IDispatch,))[0]
    if gencache.is_readonly:
        #fix for "freezed" app: py2exe.org/index.cgi/UsingEnsureDispatch
        gencache.is_readonly = False
        gencache.Rebuild()
    try:
        return gencache.EnsureDispatch(clsid)
    except (KeyError, AttributeError):  # no attribute 'CLSIDToClassMap'
        # something went wrong, reset cache
        shutil.rmtree(gencache.GetGeneratePath())
        for i in [i for i in sys.modules if i.startswith("win32com.gen_py.")]:
            del sys.modules[i]
        return gencache.EnsureDispatch(clsid)

wdApp = EnsureDispatchEx("Word.Application")

Upd: improved version resets cache on error

Arnab Ghosal · Accepted Answer · 2012-01-05 08:02:14Z

0

Why don't you do it like this?

from win32com import client
excel=client.Dispatch("Excel.Application")

edited Jan 5, 2012 at 8:02

answered Jan 3, 2012 at 13:09

Arnab Ghosal

5212 gold badges4 silver badges12 bronze badges

2 Comments

supermitch Over a year ago

If you don't run the make.py to generate a "static com proxy" then EnsureDispatch is required to access the win32com.constants. See this link: timgolden.me.uk/python/win32_how_do_i/… Furthermore, Dispatch doesn't solve his problem, the solution is DispatchEx()

ivan_pozdeev Over a year ago

This won't start a new Excel process if one is already running as the same user. See stackoverflow.com/questions/52571993/…

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