cleaner way to write this try/except statement?

[John Salerno]

The code to look at is the try statement in the NumbersValidator class, 
just a few lines down. Is this a clean way to write it? i.e. is it okay 
to have all those return statements? Is this a good use of try? Etc.

Thanks.

----------------------------

import wx


class NumbersValidator(wx.PyValidator):

     def __init__(self):
         wx.PyValidator.__init__(self)

     def Clone(self):
         return NumbersValidator()

     def Validate(self, parent):
         text_ctrl = self.GetWindow()
         text = text_ctrl.GetValue()

         try:
             if not text or int(text) <= 0:
                 wx.MessageBox('Enter a valid time.', 'Invalid time 

                               entered', wx.OK | wx.ICON_ERROR)
                 return False
             else:
                 return True
         except ValueError, error:
             wx.MessageBox('Enter a valid time.', 'Invalid time entered',
                           wx.OK | wx.ICON_ERROR)
             return False

     def TransferToWindow(self):
         return True

     def TransferFromWindow(self):
         return True


class Timer(wx.Frame):

     def __init__(self):
         wx.Frame.__init__(self, None, wx.ID_ANY, 'Timer',
                           style=wx.DEFAULT_FRAME_STYLE ^ wx.RESIZE_BORDER
                           ^ wx.MAXIMIZE_BOX)
         self.panel = wx.Panel(self)

         mainSizer = wx.BoxSizer(wx.VERTICAL)
         inputSizer = wx.BoxSizer(wx.HORIZONTAL)

         self.progress = wx.Gauge(self.panel, wx.ID_ANY, 100, size=(300, 
20))
         self.status = wx.StaticText(self.panel, wx.ID_ANY, 'Enter a time.')
         prompt = wx.StaticText(self.panel, wx.ID_ANY, 'Time to wait:')
         self.input = wx.TextCtrl(self.panel, wx.ID_ANY, size=(20, 20),
                                  validator=NumbersValidator())
         self.start = wx.Button(self.panel, wx.ID_ANY, 'Start')
         self.reset = wx.Button(self.panel, wx.ID_ANY, 'Reset')
         self.reset.Disable()
         self.sound = wx.Sound(r'C:\Windows\Media\notify.wav')
         self.timer = wx.Timer(self)

         mainSizer.Add(self.progress, flag=wx.ALIGN_CENTER | wx.ALL ^ 
wx.BOTTOM,
                       border=10)
         mainSizer.Add(self.status, flag=wx.ALIGN_CENTER | wx.ALL, 
border=10)
         mainSizer.Add(inputSizer, flag=wx.ALIGN_CENTER | wx.BOTTOM, 
border=10)
         inputSizer.Add(prompt, flag=wx.ALIGN_CENTER)
         inputSizer.Add(self.input, flag=wx.ALIGN_CENTER | wx.LEFT | 
wx.RIGHT,
                        border=5)
         inputSizer.Add(self.start, flag=wx.ALIGN_CENTER)
         inputSizer.Add(self.reset, flag=wx.ALIGN_CENTER)

         self.Bind(wx.EVT_TEXT_ENTER, self.OnStart, self.input)
         self.Bind(wx.EVT_BUTTON, self.OnStart, self.start)
         self.Bind(wx.EVT_TIMER, self.OnTimer, self.timer)
         self.Bind(wx.EVT_BUTTON, self.OnReset, self.reset)

         self.panel.SetSizer(mainSizer)
         mainSizer.Fit(self)

     def OnStart(self, event):
         if self.panel.Validate():
             self.time = int(self.input.GetValue())
             self.minutes_passed = 1
             self.minutes_remaining = self.time - 1
             self.start.Disable()
             self.input.Disable()
             self.reset.Enable()
             self.status.SetLabel('%s minute(s) remaining.' % self.time)
             self.timer.Start(1000)

     def OnReset(self, event):
         if self.timer.IsRunning():
             self.timer.Stop()
         self.input.Clear()
         self.input.Enable()
         self.start.Enable()
         self.reset.Disable()
         self.status.SetLabel('Enter a new time.')
         self.progress.SetValue(0)
         self.minutes_passed = 1

     def OnTimer(self, event):
         if self.minutes_remaining != 0:
             self.progress.SetValue(self.minutes_passed * 100 / self.time)
             self.status.SetLabel('%s minute(s) remaining.' % 
self.minutes_remaining)
             self.minutes_passed += 1
             self.minutes_remaining -= 1
         else:
             self.timer.Stop()
             self.progress.SetValue(self.minutes_passed * 100 / self.time)
             self.status.SetLabel('%s minute(s) have elapsed.' % self.time)
             wx.Sound.Play(self.sound)


class MyApp(wx.App):

     def OnInit(self):
         frame = Timer()
         self.SetTopWindow(frame)
         frame.Show()
         return True


if __name__ == '__main__':
     app = MyApp(False)
     app.MainLoop()