Issue 7975: in python 2.6 bsddb.dbshelve switched from DictMixin to

MutableMapping, and thereby lost functionality because the replacement
functionality was implemented incorrectly or incompletely).  Since bsddb
isn't in py3k, this patch just goes back to using DictMixin in order to
correct the regression.

Lib/bsddb/dbshelve.py

@@ -59,16 +59,11 @@ else:
         return cPickle.dumps(object, bin=protocol)
 
 
-if sys.version_info[0:2] <= (2, 5) :
-    try:
-        from UserDict import DictMixin
-    except ImportError:
-        # DictMixin is new in Python 2.3
-        class DictMixin: pass
-    MutableMapping = DictMixin
-else :
-    import collections
-    MutableMapping = collections.MutableMapping
+try:
+    from UserDict import DictMixin
+except ImportError:
+    # DictMixin is new in Python 2.3
+    class DictMixin: pass
 
 #------------------------------------------------------------------------
 
@@ -111,7 +106,7 @@ def open(filename, flags=db.DB_CREATE, mode=0660, filetype=db.DB_HASH,
 class DBShelveError(db.DBError): pass
 
 
-class DBShelf(MutableMapping):
+class DBShelf(DictMixin):
     """A shelf to hold pickled objects, built upon a bsddb DB object.  It
     automatically pickles/unpickles data objects going to/from the DB.
     """
@@ -162,10 +157,6 @@ class DBShelf(MutableMapping):
         else:
             return self.db.keys()
 
-    if sys.version_info[0:2] >= (2, 6) :
-        def __iter__(self) :
-            return self.db.__iter__()
-
 
     def open(self, *args, **kwargs):
         self.db.open(*args, **kwargs)

Misc/NEWS

@@ -30,6 +30,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #7975: correct regression in dict methods supported by bsddb.dbshelve.
+
 - Issue #7959: ctypes callback functions are now registered correctly
   with the cylce garbage collector.