def _edit_category(self, cat_name, new_item_list):
user = users.get_current_user()
categories = list(db.GqlQuery('SELECT * from Category where owner=:1 AND name=:2', user, cat_name))
category = categories[0]
old_item_list = []
for item in category.items:
old_item_list.append(item.name)
items_to_add = list(set(new_item_list) - set(old_item_list))
items_to_delete = list(set(old_item_list) - set(new_item_list))
for item_name in items_to_add:
item = Item(name=item_name, category=category, wins=0, losses=0)
item.put()
deleted_items = category.items.filter('name IN', items_to_delete)
for item in deleted_items:
item.delete()
