implement missing inequality on WeakSet

Lib/_weakrefset.py

@@ -171,6 +171,12 @@ class WeakSet(object):
             return NotImplemented
         return self.data == set(ref(item) for item in other)
 
+    def __ne__(self, other):
+        opposite = self.__eq__(other)
+        if opposite is NotImplemented:
+            return NotImplemented
+        return not opposite
+
     def symmetric_difference(self, other):
         newset = self.copy()
         newset.symmetric_difference_update(other)

Lib/test/test_weakset.py

@@ -351,6 +351,12 @@ class TestWeakSet(unittest.TestCase):
         self.assertFalse(self.s == tuple(self.items))
         self.assertFalse(self.s == 1)
 
+    def test_ne(self):
+        self.assertTrue(self.s != set(self.items))
+        s1 = WeakSet()
+        s2 = WeakSet()
+        self.assertFalse(s1 != s2)
+
     def test_weak_destroy_while_iterating(self):
         # Issue #7105: iterators shouldn't crash when a key is implicitly removed
         # Create new items to be sure no-one else holds a reference

Misc/NEWS

@@ -15,6 +15,8 @@ Core and Builtins
 Library
 -------
 
+- Implement inequality on weakref.WeakSet.
+
 - Issue #17981: Closed socket on error in SysLogHandler.
 
 - Issue #17754: Make ctypes.util.find_library() independent of the locale.