Mark Dickinson <dicki...@gmail.com> added the comment: Here's the documentation, which I think explains all this clearly: briefly, `return NotImplemented` and `raise NotImplementedError` are the normal usages. `raise NotImplemented` doesn't make sense, and shouldn't be used: it'll end up raising a `TypeError`, sine `NotImplemented` is neither a subclass nor an instance of BaseException.
NotImplemented: https://docs.python.org/3.7/library/constants.html#NotImplemented NotImplementedError: https://docs.python.org/3.7/library/exceptions.html#NotImplementedError Almost all of the grep results you're seeing do follow the expected patterns (either `return NotImplemented` or `raise NotImplementedError`, but a quick grep does show some questionable uses of `raise NotImplemented` in the standard library: MacBook-Pro:cpython mdickinson$ grep -r . -e raise --include=\*.py | grep "\bNotImplemented\b" ./Lib/asyncio/transports.py: The implementation here raises NotImplemented for every method ./Lib/idlelib/debugger_r.py: raise NotImplemented("dict_keys not public or pickleable") ./Lib/ssl.py: raise NotImplemented("Can't dup() %s instances" % The other way around also turns up an odd-looking `return NotImplementedError` (along with a false positive): MacBook-Pro:cpython mdickinson$ grep -r . -e return --include=\*.py | grep "\bNotImplementedError\b" ./Lib/ctypes/test/test_simplesubclasses.py: return NotImplementedError ./Lib/test/test_asyncio/test_transports.py: self.assertRaises(NotImplementedError, transport.get_returncode) ---------- nosy: +mark.dickinson _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue32464> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
