.. _mastering-telethon: ================== Mastering Telethon ================== You've come far! In this section you will learn best practices, as well as how to fix some silly (yet common) errors you may have found. Let's start with a simple one. Asyncio madness *************** We promise ``asyncio`` is worth learning. Take your time to learn it. It's a powerful tool that enables you to use this powerful library. You need to be comfortable with it if you want to master Telethon. .. code-block:: text AttributeError: 'coroutine' object has no attribute 'id' You probably had a previous version, upgraded, and expected everything to work. Remember, just add this line: .. code-block:: python import telethon.sync If you're inside an event handler you need to ``await`` **everything** that *makes a network request*. Getting users, sending messages, and nearly everything in the library needs access to the network, so they need to be awaited: .. code-block:: python @client.on(events.NewMessage) async def handler(event): print((await event.get_sender()).username) You may want to read https://lonamiwebs.github.io/blog/asyncio/ to help you understand ``asyncio`` better. I'm open for `feedback `_ regarding that blog post Entities ******** A lot of methods and requests require *entities* to work. For example, you send a message to an *entity*, get the username of an *entity*, and so on. There is an entire section on this at :ref:`entities` due to their importance. There are a lot of things that work as entities: usernames, phone numbers, chat links, invite links, IDs, and the types themselves. That is, you can use any of those when you see an "entity" is needed. You should use, **from better to worse**: 1. Input entities. For example, `event.input_chat `, `message.input_sender `, or caching an entity you will use a lot with ``entity = await client.get_input_entity(...)``. 2. Entities. For example, if you had to get someone's username, you can just use ``user`` or ``channel``. It will work. Only use this option if you already have the entity! 3. IDs. This will always look the entity up from the cache (the ``*.session`` file caches seen entities). 4. Usernames, phone numbers and links. The cache will be used too (unless you force a `client.get_entity() `), but may make a request if the username, phone or link has not been found yet. In short, unlike in most bot API libraries where you use the ID, you **should not** use the ID *if* you have the input entity. This is OK: .. code-block:: python async def handler(event): await client.send_message(event.sender_id, 'Hi') However, **this is better**: .. code-block:: python async def handler(event): await client.send_message(event.input_sender, 'Hi') Note that this also works for `message ` instead of ``event``. Telegram may not send the sender information, so if you want to be 99% confident that the above will work you should do this: .. code-block:: python async def handler(event): await client.send_message(await event.get_input_sender(), 'Hi') Methods are able to make network requests to get information that could be missing. Properties will never make a network request. Of course, it is convenient to IDs or usernames for most purposes. It will be fast enough and caching with `client.get_input_entity(...) ` will be a micro-optimization. However it's worth knowing, and it will also let you know if the entity cannot be found beforehand. .. note:: Sometimes Telegram doesn't send the access hash inside entities, so using `chat ` or `sender ` may not work, but `input_chat ` and `input_sender ` while making requests definitely will since that's what they exist for. If Telegram did not send information about the access hash, you will get something like "Invalid channel object" or "Invalid user object". Debugging ********* **Please enable logging**: .. code-block:: python import logging logging.basicConfig(level=logging.WARNING) Change it for ``logging.DEBUG`` if you are asked for logs. It will save you a lot of headaches and time when you work with events. This is for errors. Debugging is *really* important. Telegram's API is really big and there is a lot of things that you should know. Such as, what attributes or fields does a result have? Well, the easiest thing to do is printing it: .. code-block:: python user = client.get_entity('Lonami') print(user) That will show a huge line similar to the following: .. code-block:: python User(id=10885151, is_self=False, contact=False, mutual_contact=False, deleted=False, bot=False, bot_chat_history=False, bot_nochats=False, verified=False, restricted=False, min=False, bot_inline_geo=False, access_hash=123456789012345678, first_name='Lonami', last_name=None, username='Lonami', phone=None, photo=UserProfilePhoto(photo_id=123456789012345678, photo_small=FileLocation(dc_id=4, volume_id=1234567890, local_id=1234567890, secret=123456789012345678), photo_big=FileLocation(dc_id=4, volume_id=1234567890, local_id=1234567890, secret=123456789012345678)), status=UserStatusOffline(was_online=datetime.datetime(2018, 1, 2, 3, 4, 5, tzinfo=datetime.timezone.utc)), bot_info_version=None, restriction_reason=None, bot_inline_placeholder=None, lang_code=None) That's a lot of text. But as you can see, all the properties are there. So if you want the username you **don't use regex** or anything like splitting ``str(user)`` to get what you want. You just access the attribute you need: .. code-block:: python username = user.username Can we get better than the shown string, though? Yes! .. code-block:: python print(user.stringify()) Will show a much better: .. code-block:: python User( id=10885151, is_self=False, contact=False, mutual_contact=False, deleted=False, bot=False, bot_chat_history=False, bot_nochats=False, verified=False, restricted=False, min=False, bot_inline_geo=False, access_hash=123456789012345678, first_name='Lonami', last_name=None, username='Lonami', phone=None, photo=UserProfilePhoto( photo_id=123456789012345678, photo_small=FileLocation( dc_id=4, volume_id=123456789, local_id=123456789, secret=-123456789012345678 ), photo_big=FileLocation( dc_id=4, volume_id=123456789, local_id=123456789, secret=123456789012345678 ) ), status=UserStatusOffline( was_online=datetime.datetime(2018, 1, 2, 3, 4, 5, tzinfo=datetime.timezone.utc) ), bot_info_version=None, restriction_reason=None, bot_inline_placeholder=None, lang_code=None ) Now it's easy to see how we could get, for example, the ``was_online`` time. It's inside ``status``: .. code-block:: online_at = user.status.was_online You don't need to print everything to see what all the possible values can be. You can just search in http://lonamiwebs.github.io/Telethon/. Remember that you can use Python's `isinstance `_ to check the type of something. For example: .. code-block:: python from telethon import types if isinstance(user.status, types.UserStatusOffline): print(user.status.was_online) Avoiding Limits *************** Don't spam. You won't get ``FloodWaitError`` or your account banned or deleted if you use the library *for legit use cases*. Make cool tools. Don't spam! Nobody knows the exact limits for all requests since they depend on a lot of factors, so don't bother asking. Still, if you do have a legit use case and still get those errors, the library will automatically sleep when they are smaller than 60 seconds by default. You can set different "auto-sleep" thresholds: .. code-block:: python client.flood_sleep_threshold = 0 # Don't auto-sleep client.flood_sleep_threshold = 24 * 60 * 60 # Sleep always You can also except it and act as you prefer: .. code-block:: python from telethon.errors import FloodWaitError try: ... except FloodWaitError as e: print('Flood waited for', e.seconds) quit(1) VoIP numbers are very limited, and some countries are more limited too. Chat or User From Messages ************************** Although it's explicitly noted in the documentation that messages *subclass* `ChatGetter ` and `SenderGetter `, some people still don't get inheritance. When the documentation says "Bases: `telethon.tl.custom.chatgetter.ChatGetter`" it means that the class you're looking at, *also* can act as the class it bases. In this case, `ChatGetter ` knows how to get the *chat* where a thing belongs to. So, a `Message ` is a `ChatGetter `. That means you can do this: .. code-block:: python message.is_private message.chat_id message.get_chat() # ...etc `SenderGetter ` is similar: .. code-block:: python message.user_id message.get_input_user() message.user # ...etc Quite a few things implement them, so it makes sense to reuse the code. For example, all events (except raw updates) implement `ChatGetter ` since all events occur in some chat. Session Files ************* They are an important part for the library to be efficient, such as caching and handling your authorization key (or you would have to login every time!). However, some people have a lot of trouble with SQLite, especially in Windows: .. code-block:: text ...some lines of traceback 'insert or replace into entities values (?,?,?,?,?)', rows) sqlite3.OperationalError: database is locked This error occurs when **two or more clients use the same session**, that is, when you write the same session name to be used in the client: * You have two scripts running (interactive sessions count too). * You have two clients in the same script running at the same time. The solution is, if you need two clients, use two sessions. If the problem persists and you're on Linux, you can use ``fuser my.session`` to find out the process locking the file. As a last resort, you can reboot your system. If you really dislike SQLite, use a different session storage. There is an entire section covering that at :ref:`sessions`. Final Words *********** Now you are aware of some common errors and use cases, this should help you master your Telethon skills to get the most out of the library. Have fun developing awesome things!