29.08.21 23:16, Brett Cannon пише: > If you look at > https://github.com/python/cpython/blob/b11a951f16f0603d98de24fee5c023df83ea552c/Python/ceval.c#L2409-L2451 > <https://github.com/python/cpython/blob/b11a951f16f0603d98de24fee5c023df83ea552c/Python/ceval.c#L2409-L2451> > you will see that `async for` requires that the iterator returned from > `__aiter__` define `__anext__`. But if you look at aiter() which uses > PyObject_GetAiter() from > https://github.com/python/cpython/blob/f0a6fde8827d5d4f7a1c741ab1a8b206b66ffd57/Objects/abstract.c#L2741-L2759 > <https://github.com/python/cpython/blob/f0a6fde8827d5d4f7a1c741ab1a8b206b66ffd57/Objects/abstract.c#L2741-L2759> > and PyAiter_Check() from > https://github.com/python/cpython/blob/f0a6fde8827d5d4f7a1c741ab1a8b206b66ffd57/Objects/abstract.c#L2769-L2778 > <https://github.com/python/cpython/blob/f0a6fde8827d5d4f7a1c741ab1a8b206b66ffd57/Objects/abstract.c#L2769-L2778> > you will notice that aiter() requires `__anext__` *and* `__aiter__` on > the async iterator that gets returned from __aiter__. > > Now the docs for aiter() at > https://docs.python.org/3.10/library/functions.html#aiter > <https://docs.python.org/3.10/library/functions.html#aiter> points out > that the async iterator is expected to define both methods as does the > glossary definition for "asynchronous iterator" > (https://docs.python.org/3.8/glossary.html#term-asynchronous-iterator > <https://docs.python.org/3.8/glossary.html#term-asynchronous-iterator>). > > So my question is whether the discrepancy between what `async for` > expects and what `aiter()` expects on purpose? > https://bugs.python.org/issue31861 <https://bugs.python.org/issue31861> > was the issue for creating aiter() and I didn't notice a discussion of > this difference. The key reason I'm asking is this does cause a > deviation compared to the relationship between `for` and `iter()` (which > does not require `__iter__` to be defined on the iterator, although > collections.abc.Iterator does). It also makes the glossary definition > being linked from > https://docs.python.org/3.10/reference/compound_stmts.html#the-async-for-statement > <https://docs.python.org/3.10/reference/compound_stmts.html#the-async-for-statement> > incorrect.
PyIter_Check() only checks existence of __next__, not __iter__ (perhaps for performance reasons). I just ported changes from PyPy in SQLite tests (https://github.com/python/cpython/pull/28021) because a test class with __next__ but without __iter__ passed tests on CPython but failed on PyPy. _______________________________________________ Python-Dev mailing list -- python-dev@python.org To unsubscribe send an email to python-dev-le...@python.org https://mail.python.org/mailman3/lists/python-dev.python.org/ Message archived at https://mail.python.org/archives/list/python-dev@python.org/message/VWZQPBE5SLKA5IDOGSOJYFWUDOQ7HJKS/ Code of Conduct: http://python.org/psf/codeofconduct/
