diff options
Diffstat (limited to 'Lib/abc.py')
| -rw-r--r-- | Lib/abc.py | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/Lib/abc.py b/Lib/abc.py index 515ba08f23..02e48a1bb3 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 @@ class ABCMeta(type): 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 @@ class ABCMeta(type): """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 @@ class ABCMeta(type): # 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 |