[pywin32-bugs] [ pywin32-Bugs-2052253 ] Problem calling WMI method

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Bugs item #2052253, was opened at 2008-08-15 02:06
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Ramon Garcia (ramong)
Assigned to: Nobody/Anonymous (nobody)
Summary: Problem calling WMI method

Initial Comment:
An exception is issued if a WMI method call is attempted. The following code shows it.

	wmiservice = Dispatch("WbemScripting.SWbemLocator")
	wmi = wmiservice.ConnectServer("localhost", "root\cimv2")
	moniker = r"winmgmts:" \
		"{impersonationLevel=impersonate,(Security,Backup)}!\\\\" + \
		computer + r"\root\cimv2"
	wmi = GetObject(moniker)
	log_files = wmi.ExecQuery \
		("SELECT * FROM Win32_NTEventLogFile")
	for log_file in log_files:
		base = re.sub("event$", "", log_file.FileName)
		backup_filename = base + u".evt"
		log_file.BackupEventlog(backup_filename)

The following exception is raised

  File "c:\python25\lib\site-packages\win32com\client\dynamic.py", line 495, in __getattr__
    raise pythoncom.com_error, details
com_error: (-2147352567, 'Ocurri\xf3 una excepci\xf3n.', (0, u'SWbemObjectEx', u'Invalid parameter ', None, 0, -2147217400), None)


We traced this problem to WMI issing an unexecpected return code when it is attempted to get a property that is a method. The function __getattr__ in class CDispatch tries to resolve an attribute request as an attribute first, and then, if an error is raisen by COM, as a method:

if details[0] in ERRORS_BAD_CONTEXT:
    # May be a method.
    self._olerepr_.mapFuncs[attr] = retEntry
    return self._make_method_(attr)
raise pythoncom.com_error, details

But the list of such errors seems not be enough. WMI is returning error code winerror.DISP_E_EXCEPTION in this case. We workarounded the problem adding winerror.DISP_E_EXCEPTION to ERRORS_BAD_CONTEXT in dynamic.py, but perhaps there is a more specific solution.

Best regards

Ramon Garcia
ra...@cn...
Comisin Nacional de Mercado de Valores

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