How can I call a Python macro in a cell formula in OpenOffice.Org Calc?

Question

To extend OpenOffice\'s capabilities, I\'ve defined some Python macros in a file in the user script directory (~/Library/Application Support/OpenOffice.org/3/user/Scripts/py

Answer 1

On the old OO.org forums, (super)user Villeroy posted an illustration of how to call Python functions from OO.org Basic, which can then be used in formulae. The key is to use the com.sun.star.script.provider.MasterScriptProviderFactory service as a bridge. Here is an adaptation of his solution, generalized to call arbitrary functions in arbitrary modules:

REM Keep a global reference to the ScriptProvider, since this stuff may be called many times: 
Global g_MasterScriptProvider as Object
REM Specify location of Python script, providing cell functions: 
Const URL_Main as String = "vnd.sun.star.script:" 
Const URL_Args as String = "?language=Python&location=user" 

Function invokePyFunc(file AS String, func As String, args As Array, outIdxs As Array, outArgs As Array)
   sURL = URL_Main & file & ".py$" & func & URL_Args
   oMSP = getMasterScriptProvider()
   On Local Error GoTo ErrorHandler
      oScript = oMSP.getScript(sURL)
      invokePyFunc = oScript.invoke(args, outIdxs, outArgs)
      Exit Function
   ErrorHandler:
      Dim msg As String, toFix As String
      msg = Error$
      toFix = ""
      If 1 = Err AND InStr(Error$, "an error occurred during file opening") Then
         msg = "Couldn' open the script file."
         toFix = "Make sure the 'python' folder exists in the user's Scripts folder, and that the former contains " & file & ".py."
      End If
      MsgBox msg & chr(13) & toFix, 16, "Error " & Err & " calling " & func
end Function

Function getMasterScriptProvider() 
   if isNull(g_MasterScriptProvider) then 
      oMasterScriptProviderFactory = createUnoService("com.sun.star.script.provider.MasterScriptProviderFactory") 
      g_MasterScriptProvider = oMasterScriptProviderFactory.createScriptProvider("") 
   endif 
   getMasterScriptProvider = g_MasterScriptProvider
End Function

This can then be used to create a OO.org Basic function callable in a formula. Using the example pytype:

Const libfile as String = "util"    REM functions live in util.py

Function pytype(value)
    pytype = invokePyFunc(libfile, "pytype", Array(value), Array(), Array())
End Function

Another potential implementation is to create a Python add-in. However, this is a much heavier option as it requires installing the OpenOffice SDK, and it isn't obvious to me whether this approach would work for free functions or only works for classes.