import os
import sys
import wx

class Panel(wx.Panel) :
    def __init__(self, parent, *args, **kwargs) :
        wx.Panel.__init__(self, parent, wx.ID_ANY)
        
        button4 = wx.Button(self, wx.ID_ANY, 'only vertical exapnd', name='button4', size=(200, 50))
        layout = wx.BoxSizer(wx.HORIZONTAL)
        layout.Add(button4, 0, wx.EXPAND)
        self.SetSizer(layout)
        
class TopPanel(wx.Panel) :
    def __init__(self, parent, *args, **kwargs) :
        wx.Panel.__init__(self, parent, wx.ID_ANY)
        
        button1 = wx.Button(self, wx.ID_ANY, 'ogriginal Size', name='button1', size=(200, 50))
        button2 = wx.Button(self, wx.ID_ANY, 'both vertical and horizontal expand', name='button2', size=(200, 50))
        button3 = wx.Button(self, wx.ID_ANY, 'only horizontal exapnd', name='button3', size=(200, 50))
        p = Panel(self, wx.ID_ANY)
        
        layout = wx.BoxSizer(wx.VERTICAL)
        layout.Add(button1, 0)
        layout.Add(button2, 1, flag=wx.EXPAND)        
        layout.Add(button3, 0, flag=wx.EXPAND)        

        layout.Add(p, 1, flag=wx.EXPAND)        

        self.SetSizer(layout)


class MainFrame(wx.Frame) :
    def __init__(self, *args, **kwargs) :
        super().__init__(None, title="exFrame", **kwargs)
        
        topPanel = TopPanel(self)
        layout = wx.BoxSizer(wx.VERTICAL)
        layout.Add(topPanel, 1, flag=wx.EXPAND)
        self.SetSizer(layout)
        
        self.SetSize(500,500)
        self.SetMinSize((100, 100))
        self.Center(wx.BOTH)
        self.Show()

def main() :

    app = wx.App()
    MainFrame()
    app.MainLoop()
    return

if __name__ == '__main__' :
    main()