problems with python: pywintypes.com_error

Matt Smith s0199583 at
Fri Aug 8 13:04:27 CEST 2003

Hi all,

I am VERY new to python , 3 days to be exact, but as I have been 
programming competently in Perl and C/C++ for a while now, I thought 
it would be a simple case of relearning the syntax, and in many ways 
it has been just that.

However last night as I was just about to leave work, when I came 
across an error message I had never seen before. Not only that but it 
appears that there is very little in the way of help in all the usual 
sources of information on the internet (i.e. newsgroups and forums 
and the like) So to the problem at hand...

I am calling a program called v2wreg (its a program for interfacing 
with the registers/parallel port, used, unfortunatly i think 
exclusivly, by the company I work for), I can load the program fine, 
but when I come to use any of its advanced featurs i.e. 
SetDeviceAddress or ReadRegister I get the same type of error message.

File "<COMObject v2wreg.Application>", line 2, in MakeConnection
pywintypes.com_error: (-2147352571, 'Type mismatch.', None, 1)

When I commented out the first line I knew was giving an error, I got 
the another pywintypes.com_error from the next line in my code to use 
a feature of v2wreg? 

Are these errors connected? I have looked about abit and there has 
been some mention of programs not being registered properly 
generating pywintypes.com_error errors is there anyway I can check 
what is meant to be registered?

Any light anyone could spread on this subject would be very helpful

Thanks in advance,

Matt Smith, 
2nd year Electronic & Electrical Engineer at Edinburgh University.

p.s. here is part of my code with the affected area

        serialBusToolv2wReg = win32com.client.Dispatch
("v2wreg.Application")  ##this line works and calls the app
        minimumDesiredVersion = 142
        appVersion = serialBusToolv2wReg.QueryVersion ##this line 
also works and it calls a feature of the program
        serialBusToolv2wReg.Maximize = 10 ##this line works also
        if((appVersion) < minimumDesiredVersion):print"error"
        else: print "app version is working well....'yaaay'"
        serialTransportParameters = []
        PciCardId = 0
        if(self.transpor == 'pci'):serialTransportParameters=["VPCI"
(65536+PciCardId), 0]
        elif( self.transpor == 'parallel'):serialTransportParameters=
        else: print "eeek..error"
        if(self.protocol == 'i2c'):serialTransportParameters.insert
(0, 0)
        elif(self.protocol == 'cci'):serialTransportParameters.insert
(0, 1)
        elif(self.protocol == 'v2w'):serialTransportParameters.insert
(0, 0)
        else: print "error......."
        print "serialTransportParameters->", serialTransportParameters
        success = serialBusToolv2wReg.MakeConnection
(serialTransportParameters)###this line is where the error appears
        if not (self.deviceAddress == -1):
            serialBusToolv2wReg.SetDeviceAddress = self.deviceAddress 
##this line also returns a pywintypes.com_error error
            serialIndex = win32com.client.pythoncom.VT_VARIANT = 0
            serialValue = win32com.client.pythoncom.VT_VARIANT = 0
            serialAutoInc = win32com.client.pythoncom.VT_VARIANT = 0
            success = serialBusToolv2wReg.ReadRegisterNoWrite
(self.deviceAddress, serialIndex, serialValue, serialAutoInc)
            if ((success == 0) or (serialValue = 'read failed') :
                print "read error booo \n"
            else: print "\n error"
            print success

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