Use weakrefs to hold onto classes #2521.
This also causes the _weakref module to be built into the core.
diff --git a/Lib/abc.py b/Lib/abc.py
index 515ba08..02e48a1 100644
--- a/Lib/abc.py
+++ b/Lib/abc.py
@@ -5,6 +5,7 @@
import types
+from _weakrefset import WeakSet
# Instance of old-style class
class _C: pass
@@ -95,9 +96,9 @@
abstracts.add(name)
cls.__abstractmethods__ = frozenset(abstracts)
# Set up inheritance registry
- cls._abc_registry = set()
- cls._abc_cache = set()
- cls._abc_negative_cache = set()
+ cls._abc_registry = WeakSet()
+ cls._abc_cache = WeakSet()
+ cls._abc_negative_cache = WeakSet()
cls._abc_negative_cache_version = ABCMeta._abc_invalidation_counter
return cls
@@ -128,7 +129,7 @@
"""Override for isinstance(instance, cls)."""
# Inline the cache checking when it's simple.
subclass = getattr(instance, '__class__', None)
- if subclass in cls._abc_cache:
+ if subclass is not None and subclass in cls._abc_cache:
return True
subtype = type(instance)
# Old-style instances
@@ -152,7 +153,7 @@
# Check negative cache; may have to invalidate
if cls._abc_negative_cache_version < ABCMeta._abc_invalidation_counter:
# Invalidate the negative cache
- cls._abc_negative_cache = set()
+ cls._abc_negative_cache = WeakSet()
cls._abc_negative_cache_version = ABCMeta._abc_invalidation_counter
elif subclass in cls._abc_negative_cache:
return False