improved singleton

backend/Main.py

@@ -5,7 +5,8 @@ from app.classes.Settings import SettingsManager
 from tornado.options import options
 
 if __name__ == "__main__":
-    mng = SettingsManager.get_instance()
+    mng = SettingsManager()
+    m = SettingsManager()
     tornado.options.parse_command_line()
     app = ChameleonApplication()
     print(f"Serving on port {options.port}")

backend/app/classes/Settings.py

@@ -1,30 +1,13 @@
 import os
 import json
+from Singleton import Singleton
 
 
-class SettingsManager:
+class SettingsManager(metaclass=Singleton):
 
     cams = {}
 
-    __instance = None
-
-    @staticmethod
-    def get_instance():
-
-        if not SettingsManager.__instance:
-            SettingsManager()
-
-        return SettingsManager.__instance
-
     def __init__(self):
-
-        if SettingsManager.__instance:
-            raise Exception("This class is a singleton!")
-        else:
-            SettingsManager.__instance = self
-            self._init_settings()
-
-    def _init_settings(self):
         self.settings_path = os.path.join(os.getcwd(), "settings")
         self.cams_path = os.path.join(self.settings_path, "cams")
         self._init_general_settings()

backend/app/classes/Singleton.py

@@ -0,0 +1,8 @@
+
+class Singleton(type):
+    _instances = {}
+
+    def __call__(cls, *args, **kwargs):
+        if cls not in cls._instances:
+            cls._instances[cls] = super(Singleton, cls).__call__(*args, **kwargs)
+        return cls._instances[cls]