I htink I'm getting closer to clarity here, but: let's say I have this silly helper function (similar to the one in the PEP): ## (sorry -- python2) def helper(x): if x > 2: raise StopIteration else: return x # I call that helper from both an iterator class and a generator function. class Iter(object): def __init__(self): self.x = 0 def __iter__(self): return self def next(self): if self.x == 3: raise StopIteration self.x += 1 return helper(self.x) def gen(): yield helper(1) yield helper(2) yield helper(3) # first just loop through them: for i in Iter(): print i for i in gen(): print i # they act exactly the same # then put them inside generator expression and loop through that: for j in ( i for i in gen() ): print j for j in ( i for i in Iter() ): print j # they still act exactly the same. Would this PEP chance that? would that StopIteration bubble up through the iterator class, but not through the generator function? If so then I'm -1 on the PEP. The only change made by this proposal is that StopIteration becomes,

in a generator, like any other unexpected exception.

but from the user's perspective, an iterator and a generator should look the same. And I think from the perspective of the author of a given generator function, they should look as much the same as possible-- i.e. if a StopIteration is raised internally, it will behave the same way as it would in a iterator class. It creates a

separation between "iterator protocol" (which is implemented by __next__) and "generator protocol" (which is written in the body of a function with 'yield' in it).

terminology messing me up here -- I understood the "iterator protocol" top mean the __iter__ and __next__ -- and a generator satisfies that protocol. Is there a "generator protocol" that means somethign different? Maybe that's what this whole sub-thread is about: I never thought there was such a thing as a "generator protocol", and I don't see why there should be. -Chris -- Christopher Barker, Ph.D. Oceanographer Emergency Response Division NOAA/NOS/OR&R (206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception Chris.Barker@noaa.gov