Promoting Python

[Ian Kelly]

On Wed, Apr 6, 2016 at 1:22 PM, Marko Rauhamaa <marko at pacujo.net> wrote:
> However, BartC's No-Buzzword Python doesn't have classes... If he
> allowed for types.SimpleNamespace, we could have:
>
> ========================================================================
> import types
>
> def While(predicate):
>     def __iter__():
>         return thingy
>     def __next__():
>         if thingy._exited or not predicate():
>             thingy._exited = True
>             raise StopIteration
>     thingy = types.SimpleNamespace(
>         _exited=False, __iter__=__iter__, __next__=__next__)
>     return thingy
> ========================================================================
>
> However, that results in:
>
>     TypeError: 'types.SimpleNamespace' object is not iterable
>
> Where's my bug? Or is CPython buggy? Or is it the documentation:
>
>     The iterator objects themselves are required to support the
>     following two methods, which together form the iterator protocol:
>
>     iterator.__iter__()
>
>     [...]
>
>     iterator.__next__()
>
>     <URL: https://docs.python.org/3/library/stdtypes.html#typeiter>
>
> Why is a SimpleNamespace object not an iterator even though it provides
> __iter__ and __next__?

Because Python expects those methods to be defined in the class dict,
not the instance dict. In a world with only SimpleNamespace and no
classes, I think we could reasonably expect that to work (assuming
that the iterator protocol is even still a thing in that world).