From: Jeroen Demeyer Date: Tue, 10 Sep 2019 14:01:13 +0000 (+0200) Subject: bpo-37913: document that __length_hint__ can return NotImplemented (GH-15383) X-Git-Tag: v3.9.0a1~594 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=009ef2955d91e04f62a7159a1c7ddaddbfedc3b6;p=thirdparty%2FPython%2Fcpython.git bpo-37913: document that __length_hint__ can return NotImplemented (GH-15383) --- diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst index 8813f57587f0..6b9325da2f39 100644 --- a/Doc/reference/datamodel.rst +++ b/Doc/reference/datamodel.rst @@ -2155,8 +2155,10 @@ through the container; for mappings, :meth:`__iter__` should be the same as Called to implement :func:`operator.length_hint`. Should return an estimated length for the object (which may be greater or less than the actual length). - The length must be an integer ``>=`` 0. This method is purely an - optimization and is never required for correctness. + The length must be an integer ``>=`` 0. The return value may also be + *NotImplemented*, which is treated the same as if the ``__length_hint__`` + method didn't exist at all. This method is purely an optimization and is + never required for correctness. .. versionadded:: 3.4