Problem with list control and EVT_LISTBOX

Hello,

  This is a small application I generated with wxglade to illustrate
the problem I have :

import wx

class MyFrame(wx.Frame):
    def __init__(self, *args, **kwds):
        kwds["style"] = wx.DEFAULT_FRAME_STYLE
        wx.Frame.__init__(self, *args, **kwds)
        self.lb = wx.ListBox(self, -1, choices=[str(el) for el in
xrange(20)])

        self.lb.SetSelection(0)

        sizer_1 = wx.BoxSizer(wx.VERTICAL)
        sizer_1.Add(self.lb, 1, wx.EXPAND|wx.ADJUST_MINSIZE, 0)
        self.SetSizer(sizer_1)
        sizer_1.Fit(self)
        self.Layout()

        self.Bind(wx.EVT_LISTBOX, self.OnEventListBox, self.lb)

    def OnEventListBox(self, event):
        print 'EvtListBox: %s, %s, %s, %s' % (event.GetString(),
                                                event.IsSelection(),
                                                event.GetSelection(),
                                                event.GetClientData())

if __name__ == "__main__":
    app = wx.PySimpleApp(0)
    f = MyFrame(None, -1, "")
    app.SetTopWindow(f)
    f.Show()
    app.MainLoop()

If I execute this application, it works. When I launch the application
and click for instance the third element of the list it prints :
EvtListBox: 3, True, 3, None

But I don't want to have a selected element at startup so I commented
the line self.lb.SetSelection(0). If I do that, when I launch the
application and select the the third element of the list it prints :
EvtListBox: 0, True, 0, None
EvtListBox: 3, True, 3, None

The first event of the listbox also trigger a selection of the first
element of the list. In my case it launches a heavy process that I
want to avoid. After the first selection it works well, I only have 1
event.

I'm using wx Python 2.8.10.1 (gtk2-unicode) with python 2.6.2 under
linux.

Thanks,
  Jerome