rewrite Singleton class

src/database/AltConnector.py

@@ -3,7 +3,7 @@ from utils.Singleton import Singleton
 import MySQLdb as sql
 
 
-class AltConnector(metaclass=Singleton):
+class AltConnector(Singleton):
     __connection = None
 
     @staticmethod

src/database/Connector.py

@@ -4,7 +4,7 @@ from scrapy.conf import settings
 from utils.Singleton import Singleton
 
 
-class Connector(metaclass=Singleton):
+class Connector(Singleton):
     __connection = None
     __engine = create_engine(settings['CONNECTION_STRING'])
     __Session = sessionmaker(bind=__engine)

src/utils/MetaSingleton.py

+class MetaSingleton(type):
+    _instances = {}
+
+    def __call__(cls, *args, **kwargs):
+        print('__call__ __MetaSingleton')
+        if cls not in cls._instances:
+            cls._instances[cls] = super(MetaSingleton, cls).__call__(*args, **kwargs)
+        return cls._instances[cls]

src/utils/Singleton.py

+from .MetaSingleton import MetaSingleton
 
 
-class Singleton(type):
-    _instances = {}
+class Singleton:
+    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]
\ No newline at end of file
+    def __new__(cls):
+        if not hasattr(cls, 'instance'):
+            cls.instance = super(Singleton, cls).__new__(cls)
+        return cls.instance