[Python-Dev] Re: PEP 279

[Guido van Rossum]

> I had a bit of confusion that there's not StopIteration traceback printed,
> and neither is "after that".  Apparently an uncaught StopIteration call
> just exits silently?  (I'm using 2.3a0 here, in the case that it
> matters---cvs from 2-3 weeks ago)

Is this about the example below?

> from __future__ import generators
> 
> class HaltingIterator:
>     def __init__(self, *args, **kw):
> 	self._stop = 0
> 	self._generator = self.generator(*args, **kw)
> 
>     def stop(self, arg=1):
> 	self._stop = arg
> 	self.cleanup(arg)
> 
>     def next(self):
> 	if self._stop:
> 	    raise StopIteration
> 	return self._generator.next()
> 
>     def cleanup(self, arg): pass
> 
> 
> class ExampleHaltingIterator(HaltingIterator):
>     def generator(self):
> 	a, b = 1, 1
> 	while 1:
> 	    ret = a
> 	    ret, a, b = a, b, a+b
> 	    yield ret
> 
>     def cleanup(self, arg):
> 	print "halted with", arg
> 
> x = ExampleHaltingIterator()
> 
> for i in range(10): print x.next()
> x.stop("76 trombones")
> print x.next()
> print "after that"

With current CVS this prints:

1
1
2
3
5
8
13
21
34
55
halted with 76 trombones
Traceback (most recent call last):
  File "/tmp/x.py", line 35, in ?
    print x.next()
  File "/tmp/x.py", line 14, in next
    raise StopIteration
StopIteration

--Guido van Rossum (home page: http://www.python.org/~guido/)