PythonWindowsTutorial

Using Python To Harness Windows

Advanced ? ? ?

map from one accounts structure to another analyse and trace cash flows Multidimensional analysis

5.10 What we’d like…

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5.11 Design Patterns for the COM Server

COM servers and Python apps handle some arg types differently… ? Unicode String Handling – Gotcha Number One! (hopefully goes in 1.6) # our ordinary save method for use from Python def save(self, filename): f = open(filename,'wb') cPickle.dump(self.__journal,f) f.close() # what we would need for use from COM def save(self, unicode_filename): # convert it to a python string: python_filename = str(unicode_filename) f = open(python_filename,'wb') cPickle.dump(self.__journal,f) f.close() ?

…so a single class not the best design for real apps. Others options: ? ? ?

We go for option 3: Delegate. Keeps our Python package pure and portable.

Startup Code: # comservers.py – to be expanded class COMBookSet: _reg_clsid_ = '{38CB8241-D698-11D2-B806-0060974AB8A9}' _reg_progid_ = 'Doubletalk.BookServer' _public_methods_ = ['double'] def __init__(self): self.__BookSet = doubletalk.bookset.BookSet() def double(self, arg): # trivial test function to check it is alive return arg * 2 if __name__ == '__main__': win32com.server.register.UseCommandLine(COMBookSet)

COM Base Class, Python Server Pure Python Base Class, COM Subclass COM interface, Python Delegate Wrap/Unwrap subobjects

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5.12 Visual Basic GUI Startup Code

Public BookServer As Object Private Sub MDIForm_Load() InitCOMServer frmJournal.Show End Sub Private Sub MDIForm_Unload(Cancel As Integer) CloseCOMServer End Sub Sub InitCOMServer() 'called when the program starts On Error GoTo InitCOMServer_error Set BookServer = CreateObject(\ Exit Sub InitCOMServer_error: Dim msg As String msg = \BookServer.\ \the Python \ \ MsgBox msg End End Sub Sub CloseCOMServer() Set BookServer = Nothing End Sub Sub TestCOMServer() 'just to check it is alive Dim hopefully_four As Integer hopefully_four = BookServer.Double(2) MsgBox \alive\End Sub Private Sub mnuToolsTestServer_Click() 'this helps establish if the COM server is alive 'using a minimal diagnostic function in the modMain module TestCOMServer End Sub With a little luck…

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5.13 Our first view – The Journal

Goal:

Date-Ordered List of Transactions

Python Code Needed:

# more methods for COMBookSet – must be named in _public_methods_ def load(self, filename): self.__BookSet.load(str(filename)) def count(self): # return number of transactions return len(self.__BookSet) def getTransactionString(self, index): return self.__BookSet[index].asString() Visual Basic Code – File / Open handler

Private Sub mnuFileOpen_Click() Dim sFile As String With dlgCommonDialog .DialogTitle = \ .CancelError = False 'ToDo: set the flags and attributes of the common dialog control .Filter = \ .ShowOpen If Len(.FileName) = 0 Then Exit Sub End If sFile = .FileName End With BookServer.Load sFile 'display something helpful in the Journal caption frmJournal.Caption = sFile & \Transactions\End Sub

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