From 3f10a952f6056b6797e4187bcfa1a97c21d1b3bb Mon Sep 17 00:00:00 2001
From: Raymond Hettinger <python@rcn.com>
Date: Wed, 1 Apr 2009 19:05:50 +0000
Subject: Issue #5647: MutableSet.__iand__() no longer mutates self during
iteration.
---
Lib/_abcoll.py | 7 +++----
Lib/test/test_collections.py | 25 +++++++++++++++++++++++++
Misc/NEWS | 2 ++
3 files changed, 30 insertions(+), 4 deletions(-)
diff --git a/Lib/_abcoll.py b/Lib/_abcoll.py
index 45747a6..7b01178 100644
--- a/Lib/_abcoll.py
+++ b/Lib/_abcoll.py
@@ -320,10 +320,9 @@ class MutableSet(Set):
self.add(value)
return self
- def __iand__(self, c: Container):
- for value in self:
- if value not in c:
- self.discard(value)
+ def __iand__(self, it: Iterable):
+ for value in (self - it):
+ self.discard(value)
return self
def __ixor__(self, it: Iterable):
diff --git a/Lib/test/test_collections.py b/Lib/test/test_collections.py
index 3d00973..e8d72ee 100644
--- a/Lib/test/test_collections.py
+++ b/Lib/test/test_collections.py
@@ -327,6 +327,25 @@ class TestOneTrickPonyABCs(ABCTestCase):
B.register(C)
self.failUnless(issubclass(C, B))
+class WithSet(MutableSet):
+
+ def __init__(self, it=()):
+ self.data = set(it)
+
+ def __len__(self):
+ return len(self.data)
+
+ def __iter__(self):
+ return iter(self.data)
+
+ def __contains__(self, item):
+ return item in self.data
+
+ def add(self, item):
+ self.data.add(item)
+
+ def discard(self, item):
+ self.data.discard(item)
class TestCollectionABCs(ABCTestCase):
@@ -363,6 +382,12 @@ class TestCollectionABCs(ABCTestCase):
self.validate_abstract_methods(MutableSet, '__contains__', '__iter__', '__len__',
'add', 'discard')
+ def test_issue_5647(self):
+ # MutableSet.__iand__ mutated the set during iteration
+ s = WithSet('abcd')
+ s &= WithSet('cdef') # This used to fail
+ self.assertEqual(set(s), set('cd'))
+
def test_issue_4920(self):
# MutableSet.pop() method did not work
class MySet(collections.MutableSet):
diff --git a/Misc/NEWS b/Misc/NEWS
index 2ecd85b..f003c0a 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -55,6 +55,8 @@ Core and Builtins
Library
-------
+- Issue #5647: MutableSet.__iand__() no longer mutates self during iteration.
+
- Issue #5624: Fix the _winreg module name still used in several modules.
- Issue #5628: Fix io.TextIOWrapper.read() with a unreadable buffer.
--
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