diff --git a/vnpy/trader/engine.py b/vnpy/trader/engine.py
index a2e098ee..af136dab 100644
--- a/vnpy/trader/engine.py
+++ b/vnpy/trader/engine.py
@@ -197,13 +197,11 @@ class BaseEngine(ABC):
         pass
 
 
-class LogEngine(BaseEngine):
+class LogEngine(BaseEngine, metaclass=Singleton):
     """
     Processes log event and output with logging module.
     """
 
-    __metaclass__ = Singleton
-
     def __init__(self, main_engine: MainEngine, event_engine: EventEngine):
         """"""
         super(LogEngine, self).__init__(main_engine, event_engine, "log")
diff --git a/vnpy/trader/ui/mainwindow.py b/vnpy/trader/ui/mainwindow.py
index d8c6280b..b1972f42 100644
--- a/vnpy/trader/ui/mainwindow.py
+++ b/vnpy/trader/ui/mainwindow.py
@@ -24,7 +24,7 @@ from .widget import (
     AboutDialog,
 )
 from ..engine import MainEngine
-from ..utility import get_icon_path, TRADER_PATH
+from ..utility import get_icon_path, TRADER_DIR
 
 
 class MainWindow(QtWidgets.QMainWindow):
@@ -38,7 +38,7 @@ class MainWindow(QtWidgets.QMainWindow):
         self.main_engine = main_engine
         self.event_engine = event_engine
 
-        self.window_title = f"VN Trader [{TRADER_PATH}]"
+        self.window_title = f"VN Trader [{TRADER_DIR}]"
 
         self.connect_dialogs = {}
         self.widgets = {}
diff --git a/vnpy/trader/utility.py b/vnpy/trader/utility.py
index 89c412a1..6f023259 100644
--- a/vnpy/trader/utility.py
+++ b/vnpy/trader/utility.py
@@ -14,10 +14,11 @@ from .object import BarData, TickData
 
 class Singleton(type):
     """
-    Singleton metaclass, 
+    Singleton metaclass,
 
-    class A:
-        __metaclass__ = Singleton
+    usage:
+    class A(metaclass=Singleton):
+        ...
     """
     _instances = {}
 
@@ -30,7 +31,7 @@ class Singleton(type):
         return cls._instances[cls]
 
 
-def get_path(temp_name: str):
+def _get_trader_dir(temp_name: str):
     """
     Get path where trader is running in.
     """
@@ -53,21 +54,21 @@ def get_path(temp_name: str):
     return home_path, temp_path
 
 
-TRADER_PATH, TEMP_PATH = get_path(".vntrader")
+TRADER_DIR, TEMP_DIR = _get_trader_dir(".vntrader")
 
 
 def get_file_path(filename: str):
     """
     Get path for temp file with filename.
     """
-    return TEMP_PATH.joinpath(filename)
+    return TEMP_DIR.joinpath(filename)
 
 
 def get_folder_path(folder_name: str):
     """
     Get path for temp folder with folder name.
     """
-    folder_path = TEMP_PATH.joinpath(folder_name)
+    folder_path = TEMP_DIR.joinpath(folder_name)
     if not folder_path.exists():
         folder_path.mkdir()
     return folder_path