What makes an iterator an iterator?

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On Wed, 18 Apr 2007 15:39:22 +1000, Steven D'Aprano wrote:
> I thought that an iterator was any object that follows the iterator
> protocol, that is, it has a next() method and an __iter__() method.
...
> class Parrot(object):
...
>     def __init__(self):
>         self.next = self._next()

self.next isn't a method here, it's a generator. You could do:

    def __init__(self):
          self.next = self._next().next

But, having tested, that doesn't appear to work either - I think
this is because, again, self.next is not strictly a method, it's an
attribute that happens to be callable.

The python manual gives you a possible solution:

---QUOTE http://docs.python.org/lib/typeiter.html ---
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.
---END QUOTE---

i.e., just rename your _next function to __iter__ . Your class won't
itself be an iterator, but it will be usable in for statements and so one,
and convertable to an iterator with the iter builtin.