cleaner way to write this try/except statement?

[John Salerno]

Peter Otten wrote:
> John Salerno wrote:
> 
>> 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
> 
> Here's how I might do it:
> 
> def is_positive_int_str(s):
>     try:
>         value = int(s)
>     except ValueError:
>         return False
>     return value > 0
> 
> class PositiveIntegerValidator(wx.PyValidator):
>     # ...
>     def Validate(self, parent):
>         text = self.GetWindow().GetValue()
>         if is_positive_int_str(text):
>             return True
>         wx.MessageBox(...)
>         return False
> 
> Two usability notes:
> - "Invalid time entered" is a confusing message when you actually want a
> positive integer.
> - Pop-up messages are a major annoyance. An alternative would be to change
> the text color of the control and show a hint as to what input you expect
> in a status bar.
> 
> Peter
> 

Thanks for all the help guys! I'm going to rework it a little and see 
what happens. Luckily, I'm also reading the chapter on exceptions in 
Python in a Nutshell, so maybe that will help solidify my understanding 
of how to construct them in this situation.