Inheritance in DB classes

App/database/__init__.py

@@ -3,24 +3,34 @@
 
 
 # Singleton class
-class DatabaseOperations(object):
+class DatabaseOperationsBase(object):
     __instance = None
 
-    def __new__(cls, username: str, password: str):
-        if DatabaseOperations.__instance is None:
-            DatabaseOperations.__instance = object.__new__(cls)
-        auth_provider = PlainTextAuthProvider(username=username, password=password)
-        cluster = Cluster(auth_provider=auth_provider)
-        DatabaseOperations.__instance.__session = cluster.connect()
-        DatabaseOperations.__instance.__createTables()
-        return DatabaseOperations.__instance
+    def __new__(cls, username: str=None, password: str=None):
+        if DatabaseOperationsBase.__instance is None:
+            if username is None or password is None:
+                raise ValueError("You must provide the DB user and password at least the first time")
+            DatabaseOperationsBase.__instance = object.__new__(cls)
+            auth_provider = PlainTextAuthProvider(username=username, password=password)
+            cluster = Cluster(auth_provider=auth_provider)
+            DatabaseOperationsBase.__instance.__session = cluster.connect()
+            DatabaseOperationsBase.__instance.__createTables()
+        return DatabaseOperationsBase.__instance
+
+    def getInstance(self):
+        return self.__instance
 
     def __createTables(self):
         with open("../../Design/db_script.cql", "r") as sql_script:
             queries = sql_script.read().splitlines()
             for query in queries:
                 self.__session.execute(query)
 
+
+class InsertOperations(DatabaseOperationsBase):
+    def __new__(cls, *args, **kwargs):
+        return super().__new__(cls)
+
     def registerNewUser(self, user_id: int, username: str, name: str):
         query = """INSERT INTO YouTubeMDApp.User(user_id, username, name) VALUES (%s, %s, %s);"""
         self.__session.execute(query, (user_id, username, name))
@@ -46,4 +56,4 @@ def registerNewSong(self, file_id: str, video_id: str, audio_quality: int, audio
         is_metadata_by_user) VALUES (%s, %s, %s, %s, %s, %s)
         """
         self.__session.execute(query, (file_id, video_id, audio_quality, audio_format, times_requested,
-                                       is_metadata_by_user))
+                                       is_metadata_by_user))