config, optimize: fstrings in use

freqtrade/configuration.py

@@ -62,8 +62,8 @@ class Configuration(object):
                 conf = json.load(file)
         except FileNotFoundError:
             raise OperationalException(
-                'Config file "{}" not found!'
-                ' Please create a config file or check whether it exists.'.format(path))
+                f'Config file "{path}" not found!'
+                ' Please create a config file or check whether it exists.')
 
         if 'internals' not in conf:
             conf['internals'] = {}
@@ -109,7 +109,7 @@ class Configuration(object):
                 config['db_url'] = constants.DEFAULT_DB_PROD_URL
             logger.info('Dry run is disabled')
 
-        logger.info('Using DB: "{}"'.format(config['db_url']))
+        logger.info(f'Using DB: "{config["db_url"]}"')
 
         # Check if the exchange set by the user is supported
         self.check_exchange(config)

freqtrade/optimize/__init__.py

@@ -54,11 +54,8 @@ def load_tickerdata_file(
     :return dict OR empty if unsuccesful
     """
     path = make_testdata_path(datadir)
-    pair_file_string = pair.replace('/', '_')
-    file = os.path.join(path, '{pair}-{ticker_interval}.json'.format(
-        pair=pair_file_string,
-        ticker_interval=ticker_interval,
-    ))
+    pair_s = pair.replace('/', '_')
+    file = os.path.join(path, f'{pair_s}-{ticker_interval}.json')
     gzipfile = file + '.gz'
 
     # If the file does not exist we download it when None is returned.