From 2f5b9dcc0a89cbde1499c76df81c36bfd5ef9aa8 Mon Sep 17 00:00:00 2001 From: Antti Haapala Date: Thu, 30 May 2019 23:19:29 +0300 Subject: [PATCH] bpo-30969: Fix docs about the comparison in absence of __contains__ (GH-2761) --- Doc/reference/expressions.rst | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/Doc/reference/expressions.rst b/Doc/reference/expressions.rst index 52b41929d7..8b71106152 100644 --- a/Doc/reference/expressions.rst +++ b/Doc/reference/expressions.rst @@ -1563,14 +1563,15 @@ y`` returns ``True`` if ``y.__contains__(x)`` returns a true value, and ``False`` otherwise. For user-defined classes which do not define :meth:`__contains__` but do define -:meth:`__iter__`, ``x in y`` is ``True`` if some value ``z`` with ``x == z`` is -produced while iterating over ``y``. If an exception is raised during the -iteration, it is as if :keyword:`in` raised that exception. +:meth:`__iter__`, ``x in y`` is ``True`` if some value ``z``, for which the +expression ``x is z or x == z`` is true, is produced while iterating over ``y``. +If an exception is raised during the iteration, it is as if :keyword:`in` raised +that exception. Lastly, the old-style iteration protocol is tried: if a class defines :meth:`__getitem__`, ``x in y`` is ``True`` if and only if there is a non-negative -integer index *i* such that ``x == y[i]``, and all lower integer indices do not -raise :exc:`IndexError` exception. (If any other exception is raised, it is as +integer index *i* such that ``x is y[i] or x == y[i]``, and no lower integer index +raises the :exc:`IndexError` exception. (If any other exception is raised, it is as if :keyword:`in` raised that exception). .. index:: -- 2.40.0