My first 'real' program

from wxPython.wx import *

class testdialog(wxDialog):
    def __init__(self,parent,ID,title,pos,size):
        id = wxNewId()
        wxDialog.__init__(self,parent,id,title,pos,size)
        panel = self
	#Label
        wxStaticBox(panel,-1,'Cm Value',(3,3),(120,43))
	wxStaticBox(panel,-1,'Inch Value',(3,48),(120,43))
	#Text Entry
        self.cm = wxTextCtrl(panel,-1,'',(14,18))
        self.inch = wxTextCtrl(panel,-1,'',(14,63))
	#Buttons
        wxButton(panel,10,'Count',(3,100),(120,25))
        wxButton(panel,11,'Clear',(3,125),(120,25))

        EVT_BUTTON(self,10,self.Count)
	EVT_BUTTON(self,11,self.Clear)

    def Count(self,event):
        cm = self.cm.GetValue()
        inch = self.inch.GetValue()
	try :        
            if cm=='' and inch=='':
                warning = wxMessageDialog(self,'Cannot process empty string','Error',
                                          wxOK|wxICON_INFORMATION)
                warning.ShowModal()
                warning.Destroy()
            elif cm !='' and inch!='':
                warning3 = wxMessageDialog(self,'Enter singe value only','Error',
                                          wxOK|wxICON_INFORMATION)
                warning3.ShowModal()
                warning3.Destroy()
                self.cm.Clear()
                self.inch.Clear()
                
            elif inch == '':
                inch_1 = float(cm)/2.54
                inch_a = round(inch_1,2)
                self.inch.WriteText(str(inch_a))
            elif cm == '':
                cm_1 = float(inch)*2.54
                cm_a = round(cm_1,2)
                self.cm.WriteText(str(cm_a))
        except ValueError:
            warning2 = wxMessageDialog(self,'Please enter numerical value(s) only','Error',
                                       wxOK|wxICON_INFORMATION)
            warning2.ShowModal()
            warning2.Destroy()
            self.cm.Clear()
            self.inch.Clear()           
            
	
    def Clear(self,event):
	self.cm.Clear()
	self.inch.Clear()
       	
           
class okrun(wxApp):
    def OnInit(self):
        return True

app = okrun(0)
dlg = testdialog(NULL,-1,'MIGHTconv v1(b)',(200,200),(132,180))
dlg.ShowModal()       
dlg.Destroy()