diff --git a/vnpy/app/algo_trading/algos/best_limit_algo.py b/vnpy/app/algo_trading/algos/best_limit_algo.py
index 1fc252ea..168d8e37 100644
--- a/vnpy/app/algo_trading/algos/best_limit_algo.py
+++ b/vnpy/app/algo_trading/algos/best_limit_algo.py
@@ -87,7 +87,7 @@ class BestLimitAlgo(AlgoTemplate):
         if not order.is_active():
             self.vt_orderid = ""
             self.order_price = 0
-            self.put_variables_event()   
+            self.put_variables_event()
 
     def buy_best_limit(self):
         """"""
@@ -98,7 +98,7 @@ class BestLimitAlgo(AlgoTemplate):
             self.order_price,
             order_volume,
             offset=self.offset
-        )        
+        )
 
     def sell_best_limit(self):
         """"""
@@ -109,4 +109,4 @@ class BestLimitAlgo(AlgoTemplate):
             self.order_price,
             order_volume,
             offset=self.offset
-        )         
\ No newline at end of file
+        )
diff --git a/vnpy/app/algo_trading/algos/stop_algo.py b/vnpy/app/algo_trading/algos/stop_algo.py
index 54b45bf7..14b5e94f 100644
--- a/vnpy/app/algo_trading/algos/stop_algo.py
+++ b/vnpy/app/algo_trading/algos/stop_algo.py
@@ -75,12 +75,13 @@ class StopAlgo(AlgoTemplate):
                     self.volume,
                     offset=self.offset
                 )
-                self.write_log(f"停止单已触发，代码：{self.vt_symbol}，方向：{self.direction}, 价格：{self.stop_price}，数量：{self.volume}，开平：{self.offset}")                   
+                self.write_log(
+                    f"停止单已触发，代码：{self.vt_symbol}，方向：{self.direction}, 价格：{self.stop_price}，数量：{self.volume}，开平：{self.offset}")
 
         else:
             if tick.last_price <= self.stop_price:
                 price = self.stop_price - self.price_add
-                
+
                 if tick.limit_down:
                     price = max(price, tick.limit_down)
 
@@ -90,7 +91,8 @@ class StopAlgo(AlgoTemplate):
                     self.volume,
                     offset=self.offset
                 )
-                self.write_log(f"停止单已触发，代码：{self.vt_symbol}，方向：{self.direction}, 价格：{self.stop_price}，数量：{self.volume}，开平：{self.offset}") 
+                self.write_log(
+                    f"停止单已触发，代码：{self.vt_symbol}，方向：{self.direction}, 价格：{self.stop_price}，数量：{self.volume}，开平：{self.offset}")
 
         self.put_variables_event()
 
diff --git a/vnpy/trader/utility.py b/vnpy/trader/utility.py
index d5b6168f..bdd3f93d 100644
--- a/vnpy/trader/utility.py
+++ b/vnpy/trader/utility.py
@@ -17,12 +17,12 @@ def extract_vt_symbol(vt_symbol: str):
     """
     :return: (symbol, exchange)
     """
-    symbol, exchange_str = vt_symbol.split('.')
+    symbol, exchange_str = vt_symbol.split(".")
     return symbol, Exchange(exchange_str)
 
 
 def generate_vt_symbol(symbol: str, exchange: Exchange):
-    return f'{symbol}.{exchange.value}'
+    return f"{symbol}.{exchange.value}"
 
 
 def _get_trader_dir(temp_name: str):
@@ -84,7 +84,7 @@ def load_json(filename: str):
     filepath = get_file_path(filename)
 
     if filepath.exists():
-        with open(filepath, mode='r',encoding = 'UTF-8') as f:
+        with open(filepath, mode="r", encoding="UTF-8") as f:
             data = json.load(f)
         return data
     else:
@@ -97,8 +97,13 @@ def save_json(filename: str, data: dict):
     Save data into json file in temp path.
     """
     filepath = get_file_path(filename)
-    with open(filepath, mode='w+',encoding = 'UTF-8') as f:
-        json.dump(data, f,sort_keys=True,indent =4,ensure_ascii=False)
+    with open(filepath, mode="w+", encoding="UTF-8") as f:
+        json.dump(
+            data,
+            f,
+            indent=4,
+            ensure_ascii=False
+        )
 
 
 def round_to(value: float, target: float):