Update app.py

app.py

@@ -20,7 +20,7 @@ async def on_member_join(member):
 
     welcome_list.append(member.mention)
 
-    if welcome_list.len > 4:
+    if len(welcome_list) > 4:
         channel = bot.get_channel(1100458786826747945)
         message = f'Welcome to the server, {welcome_list[0]} {welcome_list[1]} {welcome_list[2]} {welcome_list[3]}! :hugging_face:'
         await channel.send(message)