title: Prevent panels from overlapping in wxPython?
body: <p>I am just getting started with wxPython.  I have the following code:</p>
  
  <pre><code>import wx
  
  class SASFrame(wx.Frame):
      def __init__(self,parent,id,title):
  
          wx.Frame.__init__(self,parent,id,title)
          groupPanel = wx.Panel(self)
  
          st = wx.StaticText(groupPanel, -1, "Which characteristics would you like to group by?")
  
          cbAge = wx.CheckBox(groupPanel, -1, "Age")
          cbMarket = wx.CheckBox(groupPanel,-1, "Market")
  
          groupSizer = wx.BoxSizer(wx.VERTICAL)
          groupSizer.AddMany([st,cbAge, cbMarket])
          groupPanel.SetSizer(groupSizer)
  
          summaryPanel = wx.Panel(self)
  
          st2 = wx.StaticText(summaryPanel, -1, "What would you like to summarize?")
          cbPremiums = wx.CheckBox(summaryPanel,-1, "Premiums")
          cbClaims = wx.CheckBox(summaryPanel,-1, "Claims")
  
          summarySizer = wx.BoxSizer(wx.VERTICAL)
          summarySizer.AddMany([st2,cbPremiums,cbClaims])
          summaryPanel.SetSizer(summarySizer)
  
          frameSizer = wx.BoxSizer(wx.VERTICAL)
          frameSizer.Add(groupPanel,1,wx.EXPAND)
          frameSizer.Add(summaryPanel,1,wx.EXPAND)
  
          self.SetSizer(frameSizer)
  
  class SASApp(wx.App):
      def __init__(self):
          wx.App.__init__(self)
      def OnInit(self):
          self.frame = SASFrame(parent=None,id=-1,title="HCRFM Custom Report Generator")
          self.frame.Show()
          self.SetTopWindow(self.frame)
          return True
  
  def main():
      app = SASApp()
      app.MainLoop()
  
  if __name__ == '__main__':
      main()
  </code></pre>
  
  <p>When I resize the window so that it is really small, it looks like this:</p>
  
  <p><img src="https://i.stack.imgur.com/cUcFC.png" alt="overlap"></p>
  
  <p>How can I prevent this overlapping?  Also, how can I make it so the the user cannot make the window small enough to cut off the text going horizontally? I am not sure if I should worry about the latter.</p>