Sizers VS window size

[Deltones]

Hi,

I'm trying to understand one of the wiki wxPython tutorial, and I must
admit I`m a bit baffled by sizers. If I run the following relevant
piece of code, I get the result I expect, i.e a 800x600 window being
opened (sorry for the formatting):

objFrame = MainWindow(None, -1, "Small Editor", (800, 600))

def __init__(self, parent, id, title, custom_size):
        wx.Frame.__init__(self, parent, wx.ID_ANY, title, size =
custom_size,
                          style = wx.DEFAULT_FRAME_STYLE |
wx.NO_FULL_REPAINT_ON_RESIZE)

However, if I add this part from the tutorial, I get a much smaller
window. Why is there an interference with the result I want when
adding the sizer code?

Here's the code:

# Sizer section to understand
self.sizer2 = wx.BoxSizer(wx.HORIZONTAL)
self.buttons = []

for nI in range(0, 6):
    self.buttons.append(wx.Button(self, ID_BUTTON + nI, "Button &" +
`nI`))
    self.sizer2.Add(self.buttons[nI], 1, wx.EXPAND)

self.sizer = wx.BoxSizer(wx.VERTICAL)
self.sizer.Add(self.control, 1, wx.EXPAND)
self.sizer.Add(self.sizer2, 0, wx.EXPAND)

self.SetSizer(self.sizer)
self.SetAutoLayout(1)
self.sizer.Fit(self)
# End of sizer section

Thanks

Denis