Importing WMI in a child Thread throws an error

[kyosohma]

Hi,

I am trying to create a post logon script which does various tasks,
like setup a printer based on location. While most of it works very
fast, I have a second Python script that I run that scans the PC using
WMI (among other things) and writes the following to a database: Name,
Username, Machine, IP, Login Date,CPU,Memory.

The problem I have is that since I import WMI, it takes a long time
and we have users complaining about it. So I stuck the import
statement into a separate thread and set it to a daemon so it could do
its thing in the background and the rest of the script would finish
and exit.

Unfortunately, I get the following error when I do this:

Exception in thread Thread-1:
Traceback (most recent call last):
File "C:\Python24\lib\threading.py", line 444, in __bootstrap
self.run()
File "C:\Python24\lib\threading.py", line 424, in run
self.__target(*self.__args, **self.__kwargs)
File "//serverName/Scripts/PostLogon_MT.py", line 35, in InvThread
import db_inventory
File "\\serverName\PythonPackages\Utilities\db_inventory.py", line
3, in ?
import wmi
File "C:\Python24\lib\site-packages\wmi.py", line 204, in ?
obj = GetObject ("winmgmts:")
File "C:\Python24\lib\site-packages\win32com\client\__init__.py",
line 73, in GetObject
return Moniker(Pathname, clsctx)
File "C:\Python24\lib\site-packages\win32com\client\__init__.py",
line 88, in Moniker
moniker, i, bindCtx = pythoncom.MkParseDisplayName(Pathname)
com_error: (-2147221020, 'Invalid syntax', None, None)

If I import the module without using threading, it works fine, but
takes forever. Even after it threw that error above, the process
didn't stop and I had to kill it with a control+C.

I am using Windows XP with Python 2.4. Thanks for any help you can
give.

Mike

 

[Tim Golden]

The problem I have is that since I import WMI, it takes a long time
and we have users complaining about it. So I stuck the import
statement into a separate thread and set it to a daemon so it could do
its thing in the background and the rest of the script would finish
and exit.

Two things:

1) If you run WMI in a thread, you'll need to call
pythoncom.CoInitialize first:

<code>
import pythoncom
import wmi

pythoncom.CoInitialize ()
c = wmi.WMI ()
#
# do things
#
pythoncom.CoUninitialize ()
</code>

2) If you need a bit of speed running WMI, see the post
I sent a few days ago to someone else:

http://mail.python.org/pipermail/python-win32/2007-February/005550.html

TJG

 

[kyosohma]

Two things:

1) If you run WMI in a thread, you'll need to call
pythoncom.CoInitialize first:

<code>
import pythoncom
import wmi

pythoncom.CoInitialize ()
c = wmi.WMI ()
#
# do things
#
pythoncom.CoUninitialize ()
</code>

2) If you need a bit of speed running WMI, see the post
I sent a few days ago to someone else:

http://mail.python.org/pipermail/python-win32/2007-February/005550.html

TJG

Thanks! This works for my problem. It appears to cut the real time
required for my script to run by 30-50%. I tried to figure out how to
apply your answer to the other fellow, but I am actually querying WMI
for the amount of RAM and the CPU type and I just don't see how to use
your example in these cases. I am new to the WMI paradigm.

Thanks again,

Mike

 

[Tim Golden]

Thanks! This works for my problem. It appears to cut the real time
required for my script to run by 30-50%. I tried to figure out how to
apply your answer to the other fellow, but I am actually querying WMI
for the amount of RAM and the CPU type and I just don't see how to use
your example in these cases. I am new to the WMI paradigm.

If you want to post some specific code examples, I'm
happy to talk you through possible optimisations.

TJG

 

[kyosohma]

If you want to post some specific code examples, I'm
happy to talk you through possible optimisations.

TJG

Sorry I didn't reply right away. Here's the straight WMI code I'm
using:

c = wmi.WMI()
for i in c.Win32_ComputerSystem():
mem = int(i.TotalPhysicalMemory)
compname = i.Name
for i in c.Win32_Processor ():
cputype = i.Name

This code was wrapped in your CoInitialize com objects.

Let me know if you need more code.

Mike

 

[Tim Golden]

If you want to post some specific code examples, I'm

Sorry I didn't reply right away. Here's the straight WMI code I'm
using:

c = wmi.WMI()
for i in c.Win32_ComputerSystem():
mem = int(i.TotalPhysicalMemory)
compname = i.Name
for i in c.Win32_Processor ():
cputype = i.Name

Well, don't know how much gain you'll get, but yo
could try the following quickies:

<code>
import wmi
c = wmi.WMI (find_classes=False)

for i in c.Win32_ComputerSystem (
['TotalPhysicalMemory', 'Name']
):
mem = int (i.TotalPhysicalMemory)
compnam = i.Name

for i in c.Win32_Processor (['Name']):
cputype = i.Name

</code>

If you were going to repeat these often (say, in
a loop, which doesn't seem likely given you
examples) you might gain a few nanosecs by
pulling the attribute lookup outside the loop:

<code>
import wmi
c = wmi.WMI (find_classes=False)

ComputerSystem = c.Win32_ComputerSystem
Processor = c.Win32_Processor

while True:
for computer_system in ComputerSystem (...): ...
for processor in Processor (...): ...

</code>

But, as everyone else on this list will tell you,
there's no point in optimising unless you know you
need to to, and unless you know where That's
what modules like timeit profiler are for.

TJG