Python library - WMI.py RegistryValueChangeEvent

Khyati shrivastavkhyati at gmail.com
Tue Apr 7 18:00:46 CEST 2015


Resolved:
watcher = c.watch_for(raw_wql=raw_wql,wmi_class = "RegistryValueChangeEvent")
is the right way - instead of wmi_class = __ExtrinsicEvent

Thanks, everyone.


On Tuesday, April 7, 2015 at 11:30:33 AM UTC-4, Khyati wrote:
> Thanks TJG for your reply. 
> I guess at this point the question is why is the event not returned to wmi as Extrinsic. May be I should explicitly initialize the class _wmi_watcher and set self.is_extrinsic = True?
> 
> 
> Thanks
> Khyati
> 
> On Tuesday, April 7, 2015 at 11:18:39 AM UTC-4, Tim Golden wrote:
> > On 07/04/2015 15:52, Tim Golden wrote:
> > > On 07/04/2015 15:35, Khyati wrote:
> > >> On Tuesday, April 7, 2015 at 10:31:47 AM UTC-4, Chris Angelico wrote:
> > >>> On Wed, Apr 8, 2015 at 12:15 AM, Khyati wrote:
> > >>>> Thanks for taking a look, Chris.
> > >>>> The error trace:
> > >>>> traceback (most recent call last):
> > >>>>  File "MonitorRegistry.py", line 18, in <module>
> > >>>>    process_created = watcher()
> > >>>>  File "C:\Python27\lib\site-packages\wmi.py", line 1195, in __call__
> > >>>>    handle_com_error ()
> > >>>>  File "C:\Python27\lib\site-packages\wmi.py", line 241, in handle_com_error
> > >>>>    raise klass (com_error=err)
> > >>>> _wmi: <x_wmi: Unexpected COM Error (-2147352567, 'Exception occurred.', (0, u'SWbemPropertySet', u'Not found ', None, 0, -2147217406), None)>
> > >>>
> > >>> It looks to me like this is a thin wrapper around the underlying API
> > >>> call, and you're getting back an error from the lower-level services.
> > >>> The way this reads, there might well not be an
> > >>> HKLM\Software\Temp\Name; maybe the ValueName is what's wrong here?
> > >>>
> > >>> Someone somewhere knows more than I do, but if you can't find that
> > >>> someone here on python-list, you might be able to find some help on
> > >>> Stack Overflow or another mailing list, from people who know how to do
> > >>> this kind of thing in a different language. You'd have to translate
> > >>> their suggestions back into Python, but when the wrappers are thin
> > >>> enough, that's usually not too hard.
> > >>>
> > >>> ChrisA
> > >>
> > >> HKLM\Software\Temp\Name exists since the event is caught correctly only when I change that key.
> > >> i'll keep looking :)
> > >>
> > > 
> > > Hi, Khyati.
> > > 
> > > Unfortunately, extrinsic events don't come with much information. As you
> > > can see from the MSDN description:
> > > 
> > > https://msdn.microsoft.com/en-us/library/aa390355%28v=vs.85%29.aspx
> > > 
> > > they're not linked to WMI objects internally (which the intrinsic events
> > > are) so all they can do is echo back to you details of what changed --
> > > which will usually be the thing you were asking about in the first place!
> > > 
> > > So the Python wrapper doesn't receive any TargetInstance because it's
> > > not a *WMI* event as such, linked to a WMI object; rather, it's an
> > > external event which has provided a hook for WMI to hang on to.
> > > 
> > > In this specific case, you could use the WMI Registry provider to pick
> > > up the current value of that registry value, but that wouldn't tell you
> > > what was there before or anything else. In another case, the event might
> > > be about some entirely external system -- such as the
> > > SecurityViolationEvent in the MSDN example -- which provides no WMI
> > > interface beyond the event itself.
> > > 
> > > Feel free to ask more, either on this list or on the win32-specific
> > > Python list:
> > > 
> > > https://mail.python.org/mailman/listinfo/python-win32
> > > 
> > > (I'm not often free to answer questions so best to use the public forums
> > > where more people will be able to help).
> > 
> > 
> > Forgot to say: you can simplify your code a little as well:
> > 
> > <code>
> > import wmi
> > 
> > c = wmi.WMI(namespace="root/default")
> > watcher = c.RegistryValueChangeEvent(Hive="HKEY_LOCAL_MACHINE",
> > KeyPath=r"Software\\Temp", ValueName="Name")
> > 
> > event = watcher()
> > 
> > </code>
> > 
> > TJG



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