Correct format. Add modes to benchmark script

Author: oschwald

examples/benchmark.py

@@ -13,12 +13,14 @@
 parser = argparse.ArgumentParser(description='Benchmark maxminddb.')
 parser.add_argument('--count', default=250000, type=int,
                     help='number of lookups')
+parser.add_argument('--mode', default=0, type=int,
+                    help='reader mode to use')
 parser.add_argument('--file', default='GeoIP2-City.mmdb',
                     help='path to mmdb file')
 
 args = parser.parse_args()
 
-reader = maxminddb.Reader(args.file)
+reader = maxminddb.open_database(args.file, args.mode)
 
 
 def lookup_ip_address():

maxminddb/__init__.py

@@ -31,7 +31,7 @@ def open_database(database, mode=MODE_AUTO):
         return maxminddb.extension.Reader(database)
     elif mode in (MODE_AUTO, MODE_MMAP, MODE_FILE, MODE_MEMORY):
         return maxminddb.reader.Reader(database, mode)
-    raise ValueError('Unsupported open mode: {}', mode)
+    raise ValueError('Unsupported open mode: {0}'.format(mode))
 
 
 def Reader(database):  # pylint: disable=invalid-name