Andy Wingo wrote:
> close() does not seem to have much value given that it isn't part of the
> iterators specification, and one can do any needed action by doing a
> throw() on the iterator and relying on the generator to have a finally
> block if needed.

But throwing has other unwanted effects, in general. First, you need to 
define a generator and give it a name. Then, close callers need to throw 
that exception. For this reason, Python defined a built-in exception, 
GeneratorExit.

But when we prototyped generators (ES4 days), with Python 2.5 already 
done and a good source of design experience to draw from, Igor Bukanov 
and I came to the current design that forces a return. A forced return 
runs the finallys but of course not catches, and it relieves everyone 
from a built-in exception. We killed StopIteration, it would be bad to 
add GeneratorExit back.

Igor even took the forced-return solution to python-dev and got a 
blessing from Philip J. Eby, as a better solution than GeneratorExit.

/be

Andy Wingo wrote:
> `close()` does not seem to have much value given that it isn't part of the
> iterators specification, and one can do any needed action by doing a
> `throw()` on the iterator and relying on the generator to have a finally
> block if needed.

But throwing has other unwanted effects, in general. First, you need to 
define a generator and give it a name. Then, close callers need to throw 
that exception. For this reason, Python defined a built-in exception, 
`GeneratorExit`.

But when we prototyped generators (ES4 days), with Python 2.5 already 
done and a good source of design experience to draw from, Igor Bukanov 
and I came to the current design that forces a `return`. A forced `return` 
runs the `finally`s but of course not `catch`es, and it relieves everyone 
from a built-in exception. We killed `StopIteration`, it would be bad to 
add `GeneratorExit` back.

Igor even took the forced-`return` solution to python-dev and got a 
blessing from Philip J. Eby, as a better solution than `GeneratorExit`.