Further reduce problematic default args

freqtrade/optimize/hyperopt_tools.py

@@ -237,8 +237,10 @@ class HyperoptTools:
                 result_dict.update(all_space_params)
 
     @staticmethod
-    def _params_pretty_print(params, space: str, header: str, non_optimized={}) -> None:
-        if space in params or space in non_optimized:
+    def _params_pretty_print(
+            params, space: str, header: str, non_optimized: Optional[Dict] = None) -> None:
+
+        if space in params or (non_optimized and space in non_optimized):
             space_params = HyperoptTools._space_params(params, space, 5)
             no_params = HyperoptTools._space_params(non_optimized, space, 5)
             appendix = ''

freqtrade/optimize/optimize_reports/bt_output.py

@@ -278,7 +278,7 @@ def text_table_add_metrics(strat_results: Dict) -> str:
 
 
 def show_backtest_result(strategy: str, results: Dict[str, Any], stake_currency: str,
-                         backtest_breakdown=[]):
+                         backtest_breakdown: List[str]):
     """
     Print results for one strategy
     """

freqtrade/rpc/api_server/ws/channel.py

@@ -152,7 +152,7 @@ class WebSocketChannel:
         """
         return self._closed.is_set()
 
-    def set_subscriptions(self, subscriptions: List[str] = []) -> None:
+    def set_subscriptions(self, subscriptions: List[str]) -> None:
         """
         Set which subscriptions this channel is subscribed to
 

freqtrade/rpc/rpc.py

@@ -155,7 +155,7 @@ class RPC:
         }
         return val
 
-    def _rpc_trade_status(self, trade_ids: List[int] = []) -> List[Dict[str, Any]]:
+    def _rpc_trade_status(self, trade_ids: Optional[List[int]] = None) -> List[Dict[str, Any]]:
         """
         Below follows the RPC backend it is prefixed with rpc_ to raise awareness that it is
         a remotely exposed function