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| -rw-r--r-- | Doc/reference/datamodel.rst | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst index 8813f57..c6c6e40 100644 --- a/Doc/reference/datamodel.rst +++ b/Doc/reference/datamodel.rst @@ -2155,7 +2155,9 @@ 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 + The length must be an integer ``>=`` 0. The return value may also be + :const:`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 |