Try/except vs. if/else

[Hung Jung Lu]

Tim Rowe <tim at remove_if_not_spam.digitig.co.uk> wrote in message news:<u941nvg94ae04ajndvbjs2hlqc9l5lemqh at 4ax.com>...
> On Tue, 23 Sep 2003 11:10:49 -0400, Shu-Hsien Sheu <sheu at bu.edu>
> wrote:
> 
> >In my understanding, using try/except rather than if/else is more 
> >pythonic. 
> 
> Rule of thumb: when the block of code is still doing what it's
> supposed to do, use if/else. If it's failing to do what it's supposed
> to do, use try/except. "except" should be an /exception/!
.....
> So try/except /only/ when something has gone wrong and you need to go
> into some sort of recovery or termination, /not/ for routine tests.

You have a valid point of view, which nonetheless is not shared by
everyone. This is a recurring subject in the newsgroup.

Python exceptions have been used for other purposes, as can be seen
from Python FAQ (e.g. "4.22 Why is there no goto?" in
http://www.python.org/doc/faq/general.html)

The "for" loop in Python is also implemented internally with
exceptions. E.g.: http://groups.google.com/groups?selm=mailman.1010884758.23378.python-list%40python.org&oe=UTF-8&output=gplain,
where it mentioned:

"... In some other languages, 'non failure' mode exceptions may be
unusual, but it's the normal idiom in Python."

regards,

Hung Jung