Refactor backend selection.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>

lib/newfol/filemanip.py

@@ -446,19 +446,17 @@ class FileStorage:
     """A file (or file-like object) in a certain format."""
     def __init__(self, fmt, filename, txnformat=None, options=None):
         self._txn = self._make_transaction_store(txnformat, options)
-        if fmt == "csv":
-            self._backend = CSVFile(filename, self._txn, options)
-        elif fmt == "qddb":
-            self._backend = QDDBFile(filename, self._txn, options)
-        elif fmt == "pickle":
-            self._backend = PickleFile(filename, self._txn, options)
-        elif fmt == "json":
-            self._backend = JSONFile(filename, self._txn, options)
-        elif fmt == "yaml":
-            self._backend = YAMLFile(filename, self._txn, options)
-        elif fmt == "raw":
-            self._backend = RawFile(filename, self._txn, options)
-        else:
+        backends = {
+            "csv": CSVFile,
+            "qddb": QDDBFile,
+            "pickle": PickleFile,
+            "json": JSONFile,
+            "yaml": YAMLFile,
+            "raw": RawFile
+        }
+        try:
+            self._backend = backends[fmt](filename, self._txn, options)
+        except KeyError:
             raise ValueError("{0}: not a supported backend".format(fmt))
     @staticmethod
     def _make_transaction_store(items, options):