[Baypiggies] Stylin' in Python..

Glen Jarvis glen at glenjarvis.com
Fri Jan 4 21:40:31 CET 2008

I've reached the level as a Python noob, where instead of struggling  
to get it to work, I'm struggling with doing things with style ;)

Since my last BayPiggies meeting, and an awesome conversation with  
JJ, I have reverently adopted PEP-8 (http://www.python.org/dev/peps/ 
pep-0008/) as a standard for all of my code. And, I've passed around  
the PEP-8 style guide in my office. Some of my peers are adopting it  

However, now, I come to some more subtle style questions. I regularly  
use pychecker and a PEP-8 checking script generously contributed to  
me from my last questions/discussion on style.

I use the example given in Learning Python (http://www.oreilly.com/ 
catalog/lpython/) by Mark Lutz for creating my own exception objects.  
However, pychecker gives me the following warning that I am catching  
a non-exception object:

 > Warnings...
 > demo.py:23: Catching a non-Exception object (General)

The sample code (from Learning Python) is included below my  
signature. My question is: Do I need to inherit a most-generic  
exception class? Or, is a non-exception class sufficient?

What does everyone think? Is this agreed upon some where? This is a  
warning from pychecker only, not an error, so I expect it's not an  
agreed upon style.... What object would I inherit? I don't really  
know the exception class Hierarchy (although I should sit down and  
give it a quick review).


glen at glenjarvis.com

"You must be the change you wish to see in the world." -M. Gandhi

class General: pass
class Specific1(General): pass
class Specific2(General): pass

def raiser0():
     X = General()           # Raise superclass instance
     raise X

def raiser1():
     X = Specific1()         # Raise subclass instance
     raise X

def raiser2():
     X = Specific2()         # Raise different subclass instance
     raise X

for func in (raiser0, raiser1, raiser2):
     except General:         # Match General or any subclass of it
         import sys
         print 'caught:', sys.exc_info()[0]
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