diff --git a/cps/__init__.py b/cps/__init__.py
index 26750d1a018ad0f9e4c442470beca785f2b71928..d26c3cdc649d54b07432825fc6cbd352e66f851f 100755
--- a/cps/__init__.py
+++ b/cps/__init__.py
@@ -1,4 +1,3 @@
-#!/usr/bin/env python
 # -*- coding: utf-8 -*-
 
 #  This file is part of the Calibre-Web (https://github.com/janeczku/calibre-web)
@@ -134,8 +133,7 @@ def get_locale():
 @babel.timezoneselector
 def get_timezone():
     user = getattr(g, 'user', None)
-    if user is not None:
-        return user.timezone
+    return user.timezone if user else None
 
 from .updater import Updater
 updater_thread = Updater()
diff --git a/cps/constants.py b/cps/constants.py
index 2bedb2822d2068587b906e6debc8427eda8eeed2..9d4938b22527ea997a2407efa9d642a66c783f91 100644
--- a/cps/constants.py
+++ b/cps/constants.py
@@ -1,4 +1,3 @@
-#!/usr/bin/env python
 # -*- coding: utf-8 -*-
 
 #   This file is part of the Calibre-Web (https://github.com/janeczku/calibre-web)
diff --git a/cps/db.py b/cps/db.py
index 1ed56234b3513ea4ad411b6ffde3acde023624fb..b9853896a54c29a2aa87b8875ff8c9b904f8c6c3 100755
--- a/cps/db.py
+++ b/cps/db.py
@@ -1,4 +1,3 @@
-#!/usr/bin/env python
 # -*- coding: utf-8 -*-
 
 #  This file is part of the Calibre-Web (https://github.com/janeczku/calibre-web)
@@ -418,7 +417,7 @@ def dispose():
 
     for attr in list(Books.__dict__.keys()):
         if attr.startswith("custom_column_"):
-            delattr(Books, attr)
+            setattr(Books, attr, None)
 
     for db_class in cc_classes.values():
         Base.metadata.remove(db_class.__table__)
diff --git a/cps/editbooks.py b/cps/editbooks.py
index 8851a0d89dde77db85e9271613ca37c60746393b..2da9991f14f90dcdae3931bbce1456c2f4d8acae 100644
--- a/cps/editbooks.py
+++ b/cps/editbooks.py
@@ -1,4 +1,3 @@
-#!/usr/bin/env python
 # -*- coding: utf-8 -*-
 
 #  This file is part of the Calibre-Web (https://github.com/janeczku/calibre-web)
@@ -301,7 +300,7 @@ def edit_cc_data(book_id, book, to_save):
                     # remove old cc_val
                     del_cc = getattr(book, cc_string)[0]
                     getattr(book, cc_string).remove(del_cc)
-                    if len(del_cc.books) == 0:
+                    if not del_cc.books or len(del_cc.books) == 0:
                         db.session.delete(del_cc)
         else:
             input_tags = to_save[cc_string].split(',')
diff --git a/cps/helper.py b/cps/helper.py
index d7308d04625b2346d232b573921569c4dfb2d996..c94093dbb898ea521cb9653b8d5d0337b33a02a8 100644
--- a/cps/helper.py
+++ b/cps/helper.py
@@ -1,4 +1,3 @@
-#!/usr/bin/env python
 # -*- coding: utf-8 -*-
 
 #  This file is part of the Calibre-Web (https://github.com/janeczku/calibre-web)
diff --git a/cps/worker.py b/cps/worker.py
index 37212873fb2bf0dac3d0bca36a903d79bb1dae4c..9744b91f9177acd5ff23e7bb3255806461071b76 100644
--- a/cps/worker.py
+++ b/cps/worker.py
@@ -1,4 +1,3 @@
-#!/usr/bin/env python
 # -*- coding: utf-8 -*-
 
 #  This file is part of the Calibre-Web (https://github.com/janeczku/calibre-web)