[Python-checkins] r61438 - in python/trunk/Lib: abc.py test/test_abc.py

Mon Mar 17 17:31:21 CET 2008

Author: jeffrey.yasskin
Date: Mon Mar 17 17:31:21 2008
New Revision: 61438
Modified:
 python/trunk/Lib/abc.py
 python/trunk/Lib/test/test_abc.py
Log:
Make isinstance(OldstyleClass, NewstyleClass) return False instead of raising
an exception. Issue reported by Joseph Armbruster.
Modified: python/trunk/Lib/abc.py
==============================================================================

--- python/trunk/Lib/abc.py	(original)
+++ python/trunk/Lib/abc.py	Mon Mar 17 17:31:21 2008
@@ -116,18 +116,18 @@
 
 def __instancecheck__(cls, instance):
 """Override for isinstance(instance, cls)."""
- # Inline the cache checking for new-style classes.
- subclass = instance.__class__
+ # Inline the cache checking when it's simple.
+ subclass = getattr(instance, '__class__', None)
 if subclass in cls._abc_cache:
 return True
 subtype = type(instance)
- if subtype is subclass:
+ if subtype is subclass or subclass is None:
 if (cls._abc_negative_cache_version ==
 ABCMeta._abc_invalidation_counter and
- subclass in cls._abc_negative_cache):
+ subtype in cls._abc_negative_cache):
 return False
 # Fall back to the subclass check.
- return cls.__subclasscheck__(subclass)
+ return cls.__subclasscheck__(subtype)
 return (cls.__subclasscheck__(subclass) or
 cls.__subclasscheck__(subtype))
 
Modified: python/trunk/Lib/test/test_abc.py
==============================================================================
--- python/trunk/Lib/test/test_abc.py	(original)
+++ python/trunk/Lib/test/test_abc.py	Mon Mar 17 17:31:21 2008
@@ -70,6 +70,17 @@
 self.assertFalse(issubclass(OldstyleClass, A))
 self.assertFalse(issubclass(A, OldstyleClass))
 
+ def test_isinstance_class(self):
+ class A:
+ __metaclass__ = abc.ABCMeta
+ class OldstyleClass:
+ pass
+ self.assertFalse(isinstance(OldstyleClass, A))
+ self.assertTrue(isinstance(OldstyleClass, type(OldstyleClass)))
+ self.assertFalse(isinstance(A, OldstyleClass))
+ # This raises a recursion depth error, but is low-priority:
+ # self.assertTrue(isinstance(A, abc.ABCMeta))
+
 def test_registration_basics(self):
 class A:
 __metaclass__ = abc.ABCMeta
