[python-win32] Trouble with list iteration / comprehension for wrapped COM objects

[Mark Hammond]

I'm not sure what's going wrong here. Does fetching the list of 
workspaces as a simple list work? That would be a workaround, and
feel free open an issue at https://github.com/mhammond/pywin32 since it 
shouldn't break that way.

Cheers

On 2025-04-18 8:33 p.m., dornech via python-win32 wrote:
> Hi there,
>
> I am working on an EXCEL wrapper to "phytonize" access to EXCEL.
>
> I create a wrapper class for all objects classes derived from abasic 
> wrapper class which mainly ensures that calls are snaked-case and 
> pyhtonized calls work. I. e. workbokkobject.SaveAs, 
> workbookobject.saveas and workbokkobject.save_as would all work. This 
> is done by overloaded __getattr__ and __setattr__ methods.
>
> The "real" EXCEL object is stored in the attribute "_xlWrapped".
>
> The overloaded __getattr__ also ensures that when retrieving f. e. a 
> workbook from the application wrapper, that the resulting EXCEL object 
> is wrapped as well. I. e. let xlapp be my wrapped EXCEL then 
> xlapp.active_workbook would return a reference to a wrapped Workbook 
> object which contains the reference to the "real" EXCEL workbook 
> object in the attribute _xlwrapped.
>
> I also overload __getitem__ to allow xlapp[1] as short for 
> xlapp.workbooks(1).
>
> Some of these classes I do extend for example to check existence of a 
> worksheet in a workbook.
>
> This as very brief introduction.
>
> Now I am struggeling with list comprehension and indexes.
>
>     # access un-wrapped EXCEL
>     print(xlapp._xlWrapped.Workbooks(1).Name)
>     print(xlapp._xlWrapped.Workbooks(2).Name)
>     for i, wb in enumerate(xlapp._xlWrapped.Workbooks):
>         print(i, wb.Name)
>
>     # access wrapped EXCEL
>     print(xlapp.Workbooks(1).Name)
>     print(xlapp.Workbooks(2).Name)
>     for i, wb in enumerate(xlapp.Workbooks):
>         print(i, wb.Name)
>
> This prints
>     WB1.xls
>     WB2.xls
>     0  WB1.xls
>     1  WB2.xls
>     WB1.xls
>     WB2.xls
>  and aborts with an windows/COM error:
>
>  ret = self._oleobj_.InvokeTypes(170, LCID, 2, (13, 0), ((12, 1),),Index
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> pywintypes.com_error: (-2147352567, 'Ausnahmefehler aufgetreten.', (0, 
> None, None, None, 0, -2147352565), None)
>
> Obviously when looping via the wrapper object the index is not 
> automatically adjusted.
> However, I must not increase the index by on in __getitem__ because 
> then the index would alway be increased.
>
> It seems, püywin32 has some special support for list comprehension and 
> index adjustment for COM objects?
> I haven't worked with an iterator before but is this the solution?
>
> Thanks in advance.
>
> Best
> Christoph
>
>
>
>
>
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> python-win32 at python.org
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