On 7 October 2016 at 17:08, Guido van Rossum <[email protected]> wrote:
> On Fri, Oct 7, 2016 at 7:47 AM, Serhiy Storchaka <[email protected]> > wrote: > > On 07.10.16 17:37, Guido van Rossum wrote: > >> > >> On Fri, Oct 7, 2016 at 6:36 AM, Serhiy Storchaka <[email protected]> > >> wrote: > >>> > >>> A number of builtin iterator classes (but not all builtin iterator > >>> classes) > >>> are registered with the Iterator ABC in Lib/_collections_abc.py. But > >>> isinstance(it, Iterable) check works without explicit registration, > >>> because > >>> Iterable has __subclasshook__ that checks iterator methods. Is there a > >>> need > >>> in explicit registrations? Or their can be safely removed? > >> > >> > >> The preferred apprach is actually inheritance; registration comes > >> next; the __subclasshook__ is a final compromise to the tradition of > >> duck typing. I think the registrations should stay. > I have a question about the registration of builtins. Currently, typing.py contains this line: ByteString.register(type(memoryview(b''))) But there are two test lines in test_collections.py self.assertNotIsInstance(memoryview(b""), ByteString) self.assertFalse(issubclass(memoryview, ByteString)) This looks like a contradiction. Which one is right? Should these tests be removed or the registration in typing.py? -- Ivan
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