collpane = wx.CollapsiblePane(self, wx.ID_ANY, "Details:") # add the pane with a zero proportion value to the 'sz' sizer which contains it sz.Add(collpane, 0, wx.GROW | wx.ALL, 5) # now add a test label in the collapsible pane using a sizer to layout it: win = collpane.GetPane() paneSz = wx.BoxSizer(wx.VERTICAL) paneSz.Add(wx.StaticText(win, wx.ID_ANY, "test!"), 1, wx.GROW | wx.ALL, 2) win.SetSizer(paneSz) paneSz.SetSizeHints(win)