[python-win32] DDE: python server/excel client - pass array?

[bob gailer]

David Haas wrote:
> I've run into a problem with DDE 

Why use DDE when COM is available?

> which, after much googling and trial
> & error, I managed to work around, but I'm pretty sure there's a
> better solution.
>
> I think the problem is this: there's currently no way for a python DDE
> server to pass an array back as a response from a DDE Request - it's
> either a string, or nothing.  Since Excel expects the response it
> receives from a DDE Request that it makes to be an array, it dies
> (with what I believe is an Error 2042) when communicating with a
> Python DDE server.
>
> If someone could give me some idea how to fix what I think is broken
> in python's DDE module, I'd greatly appreciate it.  Even better, if
> someone knows an easy way to do this which has totally escaped me, I'd
> greatly appreciate knowing how to do it. And if nothing else, someone
> else may google this response and save themselves some hassle.
> Details of my setup & what I've tried is below:
>
> I'm running Win XP, Python 2.6.1, pywin32 build 212 from Sourceforge,
> MS Excel from Office 2000.
>
> My python DDE server: basically taken verbatim from win32/demos/dde/ddeserver.py
> I think the key piece of code is in the "MyRequestTopic" class -
> namely, the call to CreateStringItem:
>
> class MyRequestTopic(object.Object):
>        def __init__(self, topicName):
>                topic = dde.CreateTopic(topicName)
>                topic.AddItem(dde.CreateStringItem(""))     <- this line
>                object.Object.__init__(self, topic)
>
> My Excel client is using a little bit of VBA to query the python DDE server:
>
> dim chan as long
> dim resp as variant
>
> chan = DDEInitiate("pyserver","request")
> resp = DDERequest(chan, "Hello")
> DDETerminate chan
>
> If I start my python DDE server, and use a python DDE client, passing
> the above request will return a valid response from the system (right
> now, it just echos back whatever it receives, so we'd get a response
> of "Hello").
> If I plug the above VBA code into Microsoft Word, the variable "resp"
> in VBA gets set to "Hello", which is the appropriate response.  Word's
> documentation says it expects a String as a response when it makes a
> DDERequest.
> However, running the above VBA code in Microsoft Excel will set the
> variable "resp" to "Error 2042".  Actually, passing any valid request
> will give me a response of "Error 2042" in Excel.  Interestingly
> enough, the documentation for Excel says it expects an Array as a
> response when it makes a DDERequest.
>
> I've tried changing the response from the DDE server into (for
> example) a list and/or a tuple, but that still gave me the same error
> in Excel.  Interestingly enough, it also would then break in Word.
>
> My workaround in Excel is to make a Word object, and then use the Word
> object to handle all the requests from my python DDE server.  It
> works, but it's not elegant.
>
> Looking through the code of ddemodule.cpp, I see a method for
> "CreateStringItem", but nothing like "CreateArrayItem", or
> "CreateGenericItem" .  Looking at the documentation for TCL's DDE
> implementation, it looks like it can pass back either a string or a
> binary array.
>
> Any ideas on either of the following two questions would be greatly appreciated:
>
> a) how I could use the current dde module to pass in something Excel could read;
> b) what extra code would need to be added to the dde module to pass back arrays;
>
>
> Thanks . . .
>
> - David
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>
>   


-- 
Bob Gailer
Chapel Hill NC 
919-636-4239