class SizeEvent(wx.Frame):

    def __init__(self, parent, id, title):
        wx.Frame.__init__(self, parent, id, title)
self.Bind(wx.EVT_SIZE, self.OnSize)
self.Centre()
self.SetSizeWH(400, 300)
self.Show(True)

def OnSize(self, event):
    hsize = event.GetSize()[0] * 0.75
Resizing a wxPython Window