1.5.2 for: else:

[John Max Skaller]

On Thu, 29 Jul 1999 08:51:15 +1200, Greg Ewing <greg.ewing at compaq.com> wrote:

>Gordon McMillan wrote:
>> 
>> But finding a match in a list, and testing whether you
>> fell off the end without finding one, is (without the else clause) a
>> much messier proposal.
>
>Not if you go about it the right way. I always
>put such loops in a procedure of their own,
>and use return:
>
>  def find_the_holy_grail(stuff):
>    for x in stuff:
>      if is_holy_grail(x):
>        return x
>    return None

Unfortunately, python lacks lexical scoping, which means this technique
cannot be easily generalised. In particular, if the loop body requires
access to the current context, you can't use a function to encapsulate it.


John Max Skaller                ph:61-2-96600850              
mailto:skaller at maxtal.com.au       10/1 Toxteth Rd 
http://www.maxtal.com.au/~skaller  Glebe 2037 NSW AUSTRALIA