wxPython - Sum 2 numbers tool

I modified a little example found on this nice website :

http://zetcode.com/wxpython/events/
The structure is simple, 2 input boxes and a button the get the result of the sum.
Obiouvsly you need wxPython installed to make it work.









This is the code:

 #!/usr/bin/python  
 # Sum of 2 numbers   
 import wx  
 class Sum_2_numbers(wx.Frame):  
     def __init__(self, parent, id, title ):  
         wx.Frame.__init__(self, parent, id, title, size=(320, 230))  
         wx.StaticText(self, -1, 'Number 1:', (30,25))  
         wx.StaticText(self, -1, 'Number 2:', (30,65))  
         wx.StaticText(self, -1, 'Sum:', (30,180))  
         self.in1 = wx.TextCtrl(self, -1, 'put a number', (100,20),size=(100,30))  
         self.in2 = wx.TextCtrl(self, -1, 'put a number', (100,60),size=(100,30))  
         self.st3 = wx.StaticText(self, -1, '', (100, 180))  
         self.Button = wx.Button(self, -1, "Sum !", wx.Point(80,120),size = (120,30))  
         self.Bind(wx.EVT_BUTTON, self.OnClick)  
         self.Centre()  
         self.Show(True)  
     def OnClick(self, event):  
         a = float(self.in1.GetValue())  
         b = float(self.in2.GetValue())  
         self.st3.SetLabel(str(a+b))  
 app = wx.App()  
 Sum_2_numbers(None, -1, 'Tool for summing 2 numbers...')  
 app.MainLoop()