python and COM

Larry Bates larry.bates at websafe.com
Fri Apr 27 22:20:47 CEST 2007


Brian Blais wrote:
> Hello,
> 
> I am trying to communicate to a Reuters feed using Python, using a
> particular set of libraries called the Adfin Real Time library.  I have
> VB code, and am trying to port it to python, and admit I really do not
> understand COM objects and being a Linux guy mainly, I don't use VB at
> all.  I've had some marginal success, but am coming up empty when it
> comes to setting up callbacks.
> 
> For example, this works:
> 
> import win32com.client
> import time
> 
> symb='GOOG.O'
> 
> mylist=win32com.client.Dispatch('AdfinXRTLib.AdxRtList')
> 
> mylist.Source="IDN_RDF"
> mylist.RegisterItems(symb,"ASK")
> mylist.StartUpdates(4)  # Mode Image
> 
> while mylist.ItemStatus(symb):
>     pass
> 
> for i in range(100):
>     m=mylist.Value(symb,"ASK")
>     print m
>     time.sleep(2)
> 
> 
> but to get it to automatically updated quotes, in VB they do something like
> 
> #================
> Public Class Form1
>   # Dimension a Public Real Time list object that is capable of handling
> events
>   # note from me:  not sure what this line does really
>   Dim WithEvents AdxList As New AdfinXRTLib.AdxRTList
> 
>   Public Sub AdxList_OnUpdate( <some args deleted>) Handles
> AdxList.OnUpdate
> 
>      do stuff with the updated data
> 
>   End Sub
> 
>   Private Sub Button1_Click(<some args deleted>)
> 
>      do stuff with button click
>   End Sub
> End Class
> #================
> 
> It seems as if the important part is the "Handles AdxList.OnUpdate",
> which I assume is basically saying "call me when AdxList.OnUpdate is
> called".  I have no idea how to get this to point to a python function,
> so I can make the AdxList.OnUpdate call python code.
> 
> Is there a tutorial somewhere about this stuff, or is there a proper
> place to ask such questions?
> 
> 
>     thanks,
> 
> 
>             Brian Blais
> 

It looks like you are correct.  This is a callback function that gets
called when the update occurs.  The only coverage of this I've found is
in "Python Programming on Win32" but it is rather brief even there.  I
have not any event driven callbacks, so I can't help all that much.
Normally you define a Python class that has methods that ADxList.OnUpdate
is expecting to be able to call.  Then depending on implementation you
either call it with an instance of that class or you may have to wrap
the instance in a COM IDispatch object by calling win32com.server.util.wrap()
around an instance of the function.  Sorry I can't be more helpful.

-Larry



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