Exception handling in Python 3.x

[John Nagle]

On 12/3/2010 5:04 AM, Steven D'Aprano wrote:
> Consider the following common exception handling idiom:
>
> def func(iterable):
>      it = iter(iterable)
>      try:
>          x = next(it)
>      except StopIteration:
>          raise ValueError("can't process empty iterable")
>      print(x)
>
> The intention is:
>
> * detect an empty iterator by catching StopIteration;
> * if the iterator is empty, raise a ValueError;
> * otherwise process the iterator.
>
> Note that StopIteration is an internal detail of no relevance whatsoever
> to the caller. Expose this is unnecessary at best and confusing at worst.

     Right.  You're not entitled to assume that StopIteration is
how a generator exits.  That's a CPyton thing; generators were
a retrofit, and that's how they were hacked in.  Other implementations
may do generators differently.

				John Nagle