[Python-ideas] PEP 479: Change StopIteration handling inside generators

[Steven D'Aprano]

On Fri, Nov 21, 2014 at 08:52:59AM -0800, Ethan Furman wrote:
> On 11/21/2014 08:30 AM, Steven D'Aprano wrote:
> > 
> > But generators and iterators *are the same thing*. (Generator functions 
> > are not iterators, but generators themselves are.) Iterators don't have 
> > a specific type, but they obey the iterator protocol:
> 
> Um, no, they aren't.  One cannot 'send()' into any ol' iterator.

"Must not support send()" has never been part of the definition of 
iterators.

The `Iterator` ABC also recognises generators as iterators:

py> def gen():
...     yield 1
...
py> from collections import Iterator
py> isinstance(gen(), Iterator)
True


and they are documented as iterators:

    Python’s generators provide a convenient way to implement
    the iterator protocol. If a container object’s __iter__() 
    method is implemented as a generator, it will automatically 
    return an iterator object (technically, a generator object) 
    supplying the __iter__() and __next__() methods.

https://docs.python.org/3/library/stdtypes.html#generator-types


I don't understand where this idea that generators aren't iterators has 
come from, unless it is confusion between the generator *function* and 
the generator object itself.


-- 
Steven