Exception as the primary error handling mechanism?

[Roy Smith]

In article <pan.2010.01.04.03.30.41 at REMOVE.THIS.cybersource.com.au>,
 Steven D'Aprano <steven at REMOVE.THIS.cybersource.com.au> wrote:

> This last one can be *very* problematic. In the early 1990s, I was 
> programming using a callback API that could only return an integer. The 
> standard way of indicating an error was to return -1. But what happens if 
> -1 is a legitimate return value, e.g. for a maths function? 

One of the truly nice features of Python is the universally distinguished 
value, None.