Enhanced the database opening conveniences:

- You can now pass storage keyword arguments to ZODB.DB and
  ZODB.connection.

- You can now pass None (rather than a storage or file name) to get
  a database with a mapping storage.

src/CHANGES.txt

@@ -24,6 +24,14 @@ New Features
   (transaction-manager attempts method) introduced in the
   ``transaction`` 1.1.0 release.
 
+- Enhanced the database opening conveniences:
+
+  - You can now pass storage keyword arguments to ZODB.DB and
+    ZODB.connection.
+
+  - You can now pass None (rather than a storage or file name) to get
+    a database with a mapping storage.
+
 Bugs Fixed
 ----------
 

src/ZODB/DB.py

@@ -386,7 +386,7 @@ class DB(object):
                  databases=None,
                  xrefs=True,
                  max_saved_oids=999,
-                 ):
+                 **storage_args):
         """Create an object database.
 
         :Parameters:
@@ -409,7 +409,10 @@ class DB(object):
         """
         if isinstance(storage, basestring):
             from ZODB import FileStorage
-            storage = ZODB.FileStorage.FileStorage(storage)
+            storage = ZODB.FileStorage.FileStorage(storage, **storage_args)
+        elif storage is None:
+            from ZODB import MappingStorage
+            storage = ZODB.MappingStorage.MappingStorage(**storage_args)
 
         # Allocate lock.
         x = threading.RLock()

src/ZODB/tests/testDB.py

@@ -161,6 +161,17 @@ def passing_a_file_name_to_DB():
     >>> db.close()
     """
 
+def passing_None_to_DB():
+    """You can pass None DB to get a MappingStorage.
+
+    (Also note that we can access DB in ZODB.)
+
+    >>> db = ZODB.DB(None)
+    >>> db.storage # doctest: +ELLIPSIS
+    <ZODB.MappingStorage.MappingStorage object at ...
+    >>> db.close()
+    """
+
 def open_convenience():
     """Often, we just want to open a single connection.
 
@@ -180,6 +191,22 @@ def open_convenience():
     >>> conn.root()
     {'x': 1}
     >>> db.close()
+
+
+    We can pass storage-specific arguments if they don't conflict with
+    DB arguments.
+
+    >>> conn = ZODB.connection('data.fs', blob_dir='blobs')
+    >>> conn.root()['b'] = ZODB.blob.Blob('test')
+    >>> transaction.commit()
+    >>> conn.close()
+
+    >>> db = ZODB.DB('data.fs', blob_dir='blobs')
+    >>> conn = db.open()
+    >>> conn.root()['b'].open().read()
+    'test'
+    >>> db.close()
+
     """
 
 if sys.version_info >= (2, 6):