Promoting Python

[Ian Kelly]

On Wed, Apr 6, 2016 at 1:59 PM, Marko Rauhamaa <marko at pacujo.net> wrote:
> Ian Kelly <ian.g.kelly at gmail.com>:
>
>> On Wed, Apr 6, 2016 at 1:22 PM, Marko Rauhamaa <marko at pacujo.net> wrote:
>>> 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.
>
> The documentation does state:
>
>    these are used to allow user-defined classes to support iteration
>
> although the rest of it only refers to objects.
>
> It seems to me CPython is being a bit too picky here. Why should it care
> if the method is a class method or an object method?

Because the purpose of a class is to define the behavior of its
instances. A function stored in an object attribute technically isn't
a method at all. It's just a function that happens to be stored in an
object attribute, i.e. *data*. Why should the behavior of a
SimpleNamespace change just because somebody decided they wanted to
store something under the name "__iter__" (or worse,
"__getattribute__")?

Also, because not having to check the instance dict for the presence
of dunder methods is faster.