Issue 8750: Fixed MutableSet's methods to correctly handle reflexive operations, namely x -= x and x ^= x
diff --git a/Lib/_abcoll.py b/Lib/_abcoll.py
index d3e23c1..cac06e0 100644
--- a/Lib/_abcoll.py
+++ b/Lib/_abcoll.py
@@ -321,18 +321,24 @@
return self
def __ixor__(self, it: Iterable):
- if not isinstance(it, Set):
- it = self._from_iterable(it)
- for value in it:
- if value in self:
- self.discard(value)
- else:
- self.add(value)
+ if it is self:
+ self.clear()
+ else:
+ if not isinstance(it, Set):
+ it = self._from_iterable(it)
+ for value in it:
+ if value in self:
+ self.discard(value)
+ else:
+ self.add(value)
return self
def __isub__(self, it: Iterable):
- for value in it:
- self.discard(value)
+ if it is self:
+ self.clear()
+ else:
+ for value in it:
+ self.discard(value)
return self
MutableSet.register(set)
diff --git a/Lib/test/test_collections.py b/Lib/test/test_collections.py
index da80baa..75d660d 100644
--- a/Lib/test/test_collections.py
+++ b/Lib/test/test_collections.py
@@ -526,6 +526,21 @@
s = MySet([5,43,2,1])
self.assertEqual(s.pop(), 1)
+ def test_issue8750(self):
+ empty = WithSet()
+ full = WithSet(range(10))
+ s = WithSet(full)
+ s -= s
+ self.assertEqual(s, empty)
+ s = WithSet(full)
+ s ^= s
+ self.assertEqual(s, empty)
+ s = WithSet(full)
+ s &= s
+ self.assertEqual(s, full)
+ s |= s
+ self.assertEqual(s, full)
+
def test_Mapping(self):
for sample in [dict]:
self.assertIsInstance(sample(), Mapping)