fixed formatting and other suggestions

lib/db.py

@@ -22,20 +22,19 @@ class DB:
 
     def schema_version(self):
         # create a cursor
-        cur = self.conn.cursor()
+        with self.conn.cursor() as cur:
 
-        # execute a statement
-        try:
-            cur.execute("SELECT MAX(version) from scheme")
-        except psycopg2.errors.UndefinedTable as error:
-            cur.close()
-            self.close()
-            self.connect()
-            return 0
+            # execute a statement
+            try:
+                cur.execute("SELECT MAX(version) from scheme")
+            except psycopg2.errors.UndefinedTable as error:
+                cur.close()
+                self.close()
+                self.connect()
+                return 0
 
-        db_version = cur.fetchone()
+            db_version = cur.fetchone()
 
-        cur.close()
         return db_version[0]
 
     def close(self):
@@ -170,15 +169,13 @@ class DB:
         if (schema_version + 1) not in schemes:
             return
         try:
-            cur = self.conn.cursor()
-            # create table one by one
-            for version, commands in schemes.items():
-                if version <= schema_version:
-                    continue
-                for command in commands:
-                    cur.execute(command)
-            # close communication with the PostgreSQL database server
-            cur.close()
+            with self.conn.cursor() as cur:
+                # create table one by one
+                for version, commands in schemes.items():
+                    if version <= schema_version:
+                        continue
+                    for command in commands:
+                        cur.execute(command)
             # commit the changes
             self.conn.commit()
         except (Exception, psycopg2.DatabaseError) as error: