What makes an iterator an iterator?

[Paul McGuire]

On Apr 18, 3:32 am, Steven D'Aprano <s... at REMOVEME.cybersource.com.au>
wrote:
> On Wed, 18 Apr 2007 06:13:39 +0000, I V wrote:
> > 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.
>
> [snip]
>
> > 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.
>
> Thanks to all those who helped, this fixed my problem.
>
> For the record, this is what I actually wanted: a four-line self-sorting
> dictionary:
>
> class SortedDict(dict):
>     def __iter__(self):
>         for key in sorted(self.keys()):
>             yield key
>
> Note that using sorted(self) does not work.
>
> Iterating over a SortedDictionary returns the keys in sorted order. This
> minimalist implementation doesn't sort the values, items or string
> representation of the dict, but they should be easy to implement.
>
> --
> Steven D'Aprano

Very neat.  Why not this?

class SortedDict(dict):
    def __iter__(self):
        return iter(sorted(self.keys()))

-- Paul