New submission from Jon Dufresne : Here: https://docs.python.org/3/reference/datamodel.html#object.__get__ The __get__ signature is defined as: object.__get__(self, instance, owner) But here: https://docs.python.org/3/howto/descriptor.html#descriptor-protocol It is defined as: descr.__get__(self, obj, type=None) It is not clear to me as a reader if all descriptors should have the owner/type argument default to None or if it should be required. If it should default to None, I think all doc examples should follow this expectation to make it clear to someone implementing a descriptor for the first time. As best I can tell, the owner/type is always passed. So perhaps the =None shouldn't be there. Grepping the CPython code, I see lots of definitions for both required and optional, adding more confusion for me. If there is a definitive answer, I'm happy to follow through by updating the docs. ---------- assignee: docs@python components: Documentation messages: 341004 nosy: docs@python, jdufresne priority: normal severity: normal status: open title: Docs: Descript __get__ signature defined differently across the docs versions: Python 2.7, Python 3.5, Python 3.6, Python 3.7, Python 3.8, Python 3.9 _______________________________________ Python tracker https://bugs.python.org/issue36743 _______________________________________