Added db.py in which the PostgreSQLDatabase class were added for working with DB.

db.py

@@ -0,0 +1,23 @@
+import psycopg2
+
+
+class PostgreSQLDatabase:
+    def __init__(self, host, database, user, password):
+        self.__host = host
+        self.__database = database
+        self.__user = user
+        self.__password = password
+
+    def execute_query(self, query):
+        connection = psycopg2.connect(
+            host=self.__host,
+            database=self.__database,
+            user=self.__user,
+            password=self.__password
+        )
+        cursor = connection.cursor()
+        cursor.execute(query)
+        result = cursor.fetchall()
+        cursor.close()
+        connection.close()
+        return result