diff --git a/database.py b/database.py
index 9604624..77a9038 100644
--- a/database.py
+++ b/database.py
@@ -60,6 +60,7 @@ class Database:
         self.conn.commit()
 
     def unsubscribe_user_by_url(self, user_id: int, url: str) -> None:
+        """Subscribe a user to the feed by url."""
         feed_id = self.find_feed_by_url(url)
         if feed_id is None:
             raise DisplayableException('Feed does not exist')
@@ -128,7 +129,7 @@ class Database:
 
     def update_feed_items(self, feed_id: int, new_items: list[FeedItem]) -> None:
         """Replace last feed items with a list items that receive."""
-        for i in range(len(new_items)):
+        for i, _ in enumerate(new_items):
             new_items[i] = [feed_id] + list(new_items[i].__dict__.values())[:-1]
 
         self.cur.execute('DELETE FROM feeds_last_items WHERE feed_id = ?', [feed_id])
diff --git a/telegram.py b/telegram.py
index 4293146..98bfd4f 100644
--- a/telegram.py
+++ b/telegram.py
@@ -59,7 +59,7 @@ class CommandProcessor:
 
         feed_list = ''
         for index, feed in enumerate(feeds, start=1):
-            feed_list += '* ' + str(index) + ': ' + f'''<a href="{feed['url']}">{feed['title']}</a''' + '\n'
+            feed_list += '* ' + str(index) + ': ' + f'''<a href="{feed['url']}">{feed['title']}</a>''' + '\n'
 
         self.bot.reply_to(message, 'Your feeds:\n' + feed_list)
 
@@ -105,7 +105,7 @@ class Notifier:
                 text=f'Updates from the {feed_title} feed:'
             )
             self.sent_counter += 1
-            
+
             for update in updates:
                 self.__send_update(chat_id, update)
                 self.sent_counter += 1
diff --git a/update_manager.py b/update_manager.py
index a928438..c8898f2 100644
--- a/update_manager.py
+++ b/update_manager.py
@@ -4,12 +4,15 @@ from telegram import Notifier
 
 
 class UpdateManager:
+    """Implement the feed update."""
+
     def __init__(self, database: Database, notifier: Notifier, rss_reader: RssReader) -> None:
         self.database: Database = database
         self.notifier: Notifier = notifier
         self.rss_reader: RssReader = rss_reader
 
     def update(self):
+        """Send new feed items to the user."""
         feeds = self.database.find_feeds()
 
         for feed_id, feed_url in feeds:
@@ -27,9 +30,10 @@ class UpdateManager:
             self.database.update_feed_items(feed_id, new_items)
 
     def __calculate_difference(self, new_items: list[FeedItem], old_items_urls: list[str]) -> list[FeedItem]:
+        """Calculate new feed items."""
         if not old_items_urls:
             return new_items
-        
+
         diff = []
 
         for item in new_items: