fix handling --exchange

freqtrade/arguments.py

@@ -443,7 +443,7 @@ class Arguments(object):
             help='Log to the file specified',
             dest='logfile',
             type=str,
-            metavar='FILE'
+            metavar='FILE',
         )
         self.parser.add_argument(
             '-c', '--config',
@@ -458,15 +458,12 @@ class Arguments(object):
             '-d', '--datadir',
             help='Path to backtest data.',
             dest='datadir',
-            default=None,
-            type=str,
             metavar='PATH',
         )
         self.parser.add_argument(
             '--pairs-file',
             help='File containing a list of pairs to download.',
             dest='pairs_file',
-            default=None,
             metavar='FILE',
         )
         self.parser.add_argument(
@@ -475,14 +472,11 @@ class Arguments(object):
             dest='days',
             type=int,
             metavar='INT',
-            default=None
         )
         self.parser.add_argument(
             '--exchange',
             help='Exchange name (default: %(default)s). Only valid if no config is provided.',
             dest='exchange',
-            type=str,
-            default='bittrex'
         )
         self.parser.add_argument(
             '-t', '--timeframes',

scripts/download_backtest_data.py

@@ -27,6 +27,9 @@ arguments.download_data_options()
 # in the command line options explicitely
 args = arguments.parse_args(no_default_config=True)
 
+# Use bittrex as default exchange
+exchange_name = args.exchange or 'bittrex'
+
 timeframes = args.timeframes
 pairs: List = []
 
@@ -46,20 +49,15 @@ if args.config:
     config['exchange']['key'] = ''
     config['exchange']['secret'] = ''
 
-    if args.exchange:
-        config['exchange']['name'] = args.exchange
-
     pairs = config['exchange']['pair_whitelist']
     timeframes = [config['ticker_interval']]
 
 else:
-    if not args.exchange:
-        sys.exit("No exchange specified.")
     config = {
         'stake_currency': '',
         'dry_run': True,
         'exchange': {
-            'name': args.exchange,
+            'name': exchange_name,
             'key': '',
             'secret': '',
             'pair_whitelist': [],
@@ -71,6 +69,13 @@ else:
     }
 
 configuration._load_logging_config(config)
+
+if args.config and args.exchange:
+    logger.warning("The --exchange option is ignored, using exchange settings from the configuration file.")
+
+# Check if the exchange set by the user is supported
+configuration.check_exchange(config)
+
 configuration._load_datadir_config(config)
 
 dl_path = Path(config['datadir'])