Working on issue #1762: Brought
./python.exe -m timeit -s 'from fractions import Fraction; f = Fraction(3, 2)' 'isinstance(3, Fraction); isinstance(f, Fraction)'
from 12.3 usec/loop to 3.44 usec/loop and
./python.exe -m timeit -s 'from fractions import Fraction' 'Fraction(3, 2)'
from 48.8 usec to 23.6 usec by avoiding genexps and sets in __instancecheck__
and inlining the common case from __subclasscheck__.
diff --git a/Lib/abc.py b/Lib/abc.py
index 1ce38a8..9d15012 100644
--- a/Lib/abc.py
+++ b/Lib/abc.py
@@ -163,8 +163,20 @@
def __instancecheck__(cls, instance):
"""Override for isinstance(instance, cls)."""
- return any(cls.__subclasscheck__(c)
- for c in set([instance.__class__, type(instance)]))
+ # Inline the cache checking for new-style classes.
+ subclass = instance.__class__
+ if subclass in cls._abc_cache:
+ return True
+ subtype = type(instance)
+ if subtype is subclass:
+ if (cls._abc_negative_cache_version ==
+ ABCMeta._abc_invalidation_counter and
+ subclass in cls._abc_negative_cache):
+ return False
+ # Fall back to the subclass check.
+ return cls.__subclasscheck__(subclass)
+ return (cls.__subclasscheck__(subclass) or
+ cls.__subclasscheck__(subtype))
def __subclasscheck__(cls, subclass):
"""Override for issubclass(subclass, cls)."""
diff --git a/Lib/test/test_abc.py b/Lib/test/test_abc.py
index 272f61d..ac5f7ee 100644
--- a/Lib/test/test_abc.py
+++ b/Lib/test/test_abc.py
@@ -83,6 +83,16 @@
self.assertEqual(issubclass(C, A), True)
self.assertEqual(isinstance(c, A), True)
+ def test_isinstance_invalidation(self):
+ class A:
+ __metaclass__ = abc.ABCMeta
+ class B(object):
+ pass
+ b = B()
+ self.assertEqual(isinstance(b, A), False)
+ A.register(B)
+ self.assertEqual(isinstance(b, A), True)
+
def test_registration_builtins(self):
class A:
__metaclass__ = abc.ABCMeta