1 files changed, 11 insertions, 1 deletions
diff --git a/Lib/shelve.py b/Lib/shelve.py
index d651b9e..c8d9cf5 100644
--- a/Lib/shelve.py
+++ b/Lib/shelve.py
@@ -64,6 +64,16 @@ import warnings
 
 __all__ = ["Shelf","BsdDbShelf","DbfilenameShelf","open"]
 
+class _ClosedDict(collections.MutableMapping):
+    'Marker for a closed dict.  Access attempts raise a ValueError.'
+
+    def closed(self, *args):
+        raise ValueError('invalid operation on closed shelf')
+    __iter__ = __len__ = __getitem__ = __setitem__ = __delitem__ = keys = closed
+
+    def __repr__(self):
+        return '<Closed Dictionary>'
+
 class Shelf(collections.MutableMapping):
     """Base class for shelf implementations.
 
@@ -127,7 +137,7 @@ class Shelf(collections.MutableMapping):
             self.dict.close()
         except AttributeError:
             pass
-        self.dict = 0
+        self.dict = _ClosedDict()
 
     def __del__(self):
         if not hasattr(self, 'writeback'):