The object.__set_name__() function (introduced in Python 3.6 by PEP-487) is mentioned in the "what's new " summary as an extension to the descriptor protocol [1] and documented in the "implementing descriptors" section [2].

However, the PEP itself states that it "adds an __set_name__ initializer for class attributes, especially if they are descriptors.". And it indeed works for plain classes where the descriptor protocol is not used at all (no __get__ or __set__ or __delete__):

----
class NotDescriptor:
    def __set_name__(self, owner, name):
        print('__set_name__ called')
            
class SomeClass:
    attr = NotDescriptor()
----

It is clear that this method is helpful when used in descriptors and that is its intended use, but other valid use-cases probably exist.

I suggest to amend the documentation to clarify that (correct me if I'm wrong) the __set_name__ is called for every class used as an attribute in an other class, not only for descriptors.

---

URLs:

[1]: https://docs.python.org/3/whatsnew/3.6.html#pep-487-descriptor-protocol-enhancements

[2]: https://docs.python.org/3/reference/datamodel.html#implementing-descriptors

You are correct that __set_name__ works for non-descriptor classes as well.

The docs for it should be moved out of the "Implementing Descriptors" section.  Also, it should have a non-descriptor example.

New changeset 94b462686b7dfabbd69cc9401037d736d71c4dc2 by Raymond Hettinger in branch 'main':
bpo-45198: __set_name__ documentation not clear about its usage with non-descriptor classes (GH-28439)
https://github.com/python/cpython/commit/94b462686b7dfabbd69cc9401037d736d71c4dc2

New changeset 7ab114bf1fa0f28ee267a4c69e597cc49a186a14 by Miss Islington (bot) in branch '3.10':
bpo-45198: __set_name__ documentation not clear about its usage with non-descriptor classes (GH-28439)
https://github.com/python/cpython/commit/7ab114bf1fa0f28ee267a4c69e597cc49a186a14

New changeset aac54ef2b30eb27f6756bbf0cdb8be2e64f2cce0 by Pablo Galindo (Miss Islington (bot)) in branch '3.10':
bpo-45198: __set_name__ documentation not clear about its usage with non-descriptor classes (GH-28439)
https://github.com/python/cpython/commit/aac54ef2b30eb27f6756bbf0cdb8be2e64f2cce0