From 8e13de6725943ce7e80bf96bc5f6bd330be428a7 Mon Sep 17 00:00:00 2001
From: Benjamin Peterson <benjamin@python.org>
Date: Fri, 21 May 2010 21:05:45 +0000
Subject: [PATCH] Merged revisions 81417 via svnmerge from
 svn+ssh://pythondev@svn.python.org/python/branches/py3k

................
  r81417 | benjamin.peterson | 2010-05-21 15:55:22 -0500 (Fri, 21 May 2010) | 9 lines

  Merged revisions 81414 via svnmerge from
  svn+ssh://pythondev@svn.python.org/python/trunk

  ........
    r81414 | benjamin.peterson | 2010-05-21 15:51:45 -0500 (Fri, 21 May 2010) | 1 line

    return NotImplemented from Mapping when comparing to a non-mapping #8729
  ........
................
---
 Lib/_abcoll.py               |  5 ++--
 Lib/test/test_collections.py | 49 +++++++++++++++++++++++++++++++++++-
 Misc/NEWS                    |  3 +++
 3 files changed, 54 insertions(+), 3 deletions(-)

diff --git a/Lib/_abcoll.py b/Lib/_abcoll.py
index a60d91e7cb..e9f06a5ed3 100644
--- a/Lib/_abcoll.py
+++ b/Lib/_abcoll.py
@@ -376,8 +376,9 @@ class Mapping(Sized, Iterable, Container):
         return ValuesView(self)
 
     def __eq__(self, other):
-        return isinstance(other, Mapping) and \
-               dict(self.items()) == dict(other.items())
+        if not isinstance(other, Mapping):
+            return NotImplemented
+        return dict(self.items()) == dict(other.items())
 
     def __ne__(self, other):
         return not (self == other)
diff --git a/Lib/test/test_collections.py b/Lib/test/test_collections.py
index ded8b70e00..33deb78ff2 100644
--- a/Lib/test/test_collections.py
+++ b/Lib/test/test_collections.py
@@ -1,6 +1,6 @@
 """Unit tests for collections.py."""
 
-import unittest, doctest
+import unittest, doctest, operator
 import inspect
 from test import support
 from collections import namedtuple, Counter, OrderedDict
@@ -230,6 +230,37 @@ class ABCTestCase(unittest.TestCase):
             self.assertRaises(TypeError, C, name)
 
 
+    def validate_comparison(self, instance):
+        ops = ['lt', 'gt', 'le', 'ge', 'ne', 'or', 'and', 'xor', 'sub']
+        operators = {}
+        for op in ops:
+            name = '__' + op + '__'
+            operators[name] = getattr(operator, name)
+
+        class Other:
+            def __init__(self):
+                self.right_side = False
+            def __eq__(self, other):
+                self.right_side = True
+                return True
+            __lt__ = __eq__
+            __gt__ = __eq__
+            __le__ = __eq__
+            __ge__ = __eq__
+            __ne__ = __eq__
+            __ror__ = __eq__
+            __rand__ = __eq__
+            __rxor__ = __eq__
+            __rsub__ = __eq__
+
+        for name, op in operators.items():
+            if not hasattr(instance, name):
+                continue
+            other = Other()
+            op(instance, other)
+            self.assertTrue(other.right_side,'Right side not called for %s.%s'
+                            % (type(instance), name))
+
 class TestOneTrickPonyABCs(ABCTestCase):
 
     def test_Hashable(self):
@@ -398,6 +429,14 @@ class TestCollectionABCs(ABCTestCase):
             self.assertTrue(isinstance(sample(), Set))
             self.assertTrue(issubclass(sample, Set))
         self.validate_abstract_methods(Set, '__contains__', '__iter__', '__len__')
+        class MySet(Set):
+            def __contains__(self, x):
+                return False
+            def __len__(self):
+                return 0
+            def __iter__(self):
+                return iter([])
+        self.validate_comparison(MySet())
 
     def test_hash_Set(self):
         class OneTwoThreeSet(Set):
@@ -461,6 +500,14 @@ class TestCollectionABCs(ABCTestCase):
             self.assertTrue(issubclass(sample, Mapping))
         self.validate_abstract_methods(Mapping, '__contains__', '__iter__', '__len__',
             '__getitem__')
+        class MyMapping(collections.Mapping):
+            def __len__(self):
+                return 0
+            def __getitem__(self, i):
+                raise IndexError
+            def __iter__(self):
+                return iter(())
+        self.validate_comparison(MyMapping())
 
     def test_MutableMapping(self):
         for sample in [dict]:
diff --git a/Misc/NEWS b/Misc/NEWS
index 23046064bb..27dd6a463d 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -54,6 +54,9 @@ C-API
 Library
 -------
 
+- Issue #8729: Return NotImplemented from collections.Mapping.__eq__ when
+  comparing to a non-mapping.
+
 - Issue #8774: tabnanny uses the encoding cookie (#coding:...) to use the
   correct encoding
 
-- 
2.40.0