.. _working-with-updates: ==================== Working with Updates ==================== The library comes with the `telethon.events` module. *Events* are an abstraction over what Telegram calls `updates`__, and are meant to ease simple and common usage when dealing with them, since there are many updates. If you're looking for the method reference, check :ref:`telethon-events-package`, otherwise, let's dive in! .. important:: The library logs by default no output, and any exception that occurs inside your handlers will be "hidden" from you to prevent the thread from terminating (so it can still deliver events). You should enable logging when working with events, at least the error level, to see if this is happening so you can debug the error. **When using updates, please enable logging:** .. code-block:: python import logging logging.basicConfig(level=logging.ERROR) .. contents:: Getting Started *************** .. code-block:: python import asyncio from telethon import TelegramClient, events client = TelegramClient('name', api_id, api_hash) @client.on(events.NewMessage) async def my_event_handler(event): if 'hello' in event.raw_text: await event.reply('hi!') asyncio.get_event_loop().run_until_complete(client.start()) client.run_until_disconnected() Not much, but there might be some things unclear. What does this code do? .. code-block:: python import asyncio from telethon import TelegramClient, events client = TelegramClient('name', api_id, api_hash) This is normal creation (of course, pass session name, API ID and hash). Nothing we don't know already. .. code-block:: python @client.on(events.NewMessage) This Python decorator will attach itself to the ``my_event_handler`` definition, and basically means that *on* a `NewMessage ` *event*, the callback function you're about to define will be called: .. code-block:: python async def my_event_handler(event): if 'hello' in event.raw_text: await event.reply('hi!') If a `NewMessage ` event occurs, and ``'hello'`` is in the text of the message, we `.reply() ` to the event with a ``'hi!'`` message. .. code-block:: python asyncio.get_event_loop().run_until_complete(client.start()) client.run_until_disconnected() Finally, this tells the client that we're done with our code. We run the ``asyncio`` loop until the client starts, and then we run it again until we are disconnected. Of course, you can do other things instead of running until disconnected. For this refer to :ref:`update-modes`. More on events ************** The `NewMessage ` event has much more than what was shown. You can access the `.sender ` of the message through that member, or even see if the message had `.media `, a `.photo ` or a `.document ` (which you could download with for example `client.download_media(event.photo) `. If you don't want to `.reply() ` as a reply, you can use the `.respond() ` method instead. Of course, there are more events such as `ChatAction ` or `UserUpdate `, and they're all used in the same way. Simply add the `@client.on(events.XYZ) ` decorator on the top of your handler and you're done! The event that will be passed always is of type ``XYZ.Event`` (for instance, `NewMessage.Event `), except for the `Raw ` event which just passes the :tl:`Update` object. Note that `.reply() ` and `.respond() ` are just wrappers around the `client.send_message() ` method which supports the ``file=`` parameter. This means you can reply with a photo if you do `event.reply(file=photo) `. You can put the same event on many handlers, and even different events on the same handler. You can also have a handler work on only specific chats, for example: .. code-block:: python import ast import random # Either a single item or a list of them will work for the chats. # You can also use the IDs, Peers, or even User/Chat/Channel objects. @client.on(events.NewMessage(chats=('TelethonChat', 'TelethonOffTopic'))) async def normal_handler(event): if 'roll' in event.raw_text: await event.reply(str(random.randint(1, 6))) # Similarly, you can use incoming=True for messages that you receive @client.on(events.NewMessage(chats='TelethonOffTopic', outgoing=True, pattern='eval (.+)')) async def admin_handler(event): expression = event.pattern_match.group(1) await event.reply(str(ast.literal_eval(expression))) You can pass one or more chats to the ``chats`` parameter (as a list or tuple), and only events from there will be processed. You can also specify whether you want to handle incoming or outgoing messages (those you receive or those you send). In this example, people can say ``'roll'`` and you will reply with a random number, while if you say ``'eval 4+4'``, you will reply with the solution. Try it! Properties vs. methods ********************** The event shown above acts just like a `custom.Message `, which means you can access all the properties it has, like ``.sender``. **However** events are different to other methods in the client, like `client.get_messages `. Events *may not* send information about the sender or chat, which means it can be ``None``, but all the methods defined in the client always have this information so it doesn't need to be re-fetched. For this reason, you have ``get_`` methods, which will make a network call if necessary. In short, you should do this: .. code-block:: python @client.on(events.NewMessage) async def handler(event): # event.input_chat may be None, use event.get_input_chat() chat = await event.get_input_chat() sender = await event.get_sender() buttons = await event.get_buttons() async def main(): async for message in client.iter_messages('me', 10): # Methods from the client always have these properties ready chat = message.input_chat sender = message.sender buttons = message.buttons Notice, properties (`message.sender `) don't need an ``await``, but methods (`message.get_sender `) **do** need an ``await``, and you should use methods in events for these properties that may need network. Events without decorators ************************* If for any reason you can't use the `@client.on ` syntax, don't worry. You can call `client.add_event_handler(callback, event) ` to achieve the same effect. Similarly, you also have `client.remove_event_handler ` and `client.list_event_handlers `. The ``event`` type is optional in all methods and defaults to `events.Raw ` for adding, and ``None`` when removing (so all callbacks would be removed). Stopping propagation of Updates ******************************* There might be cases when an event handler is supposed to be used solitary and it makes no sense to process any other handlers in the chain. For this case, it is possible to raise a `telethon.events.StopPropagation` exception which will cause the propagation of the update through your handlers to stop: .. code-block:: python from telethon.events import StopPropagation @client.on(events.NewMessage) async def _(event): # ... some conditions await event.delete() # Other handlers won't have an event to work with raise StopPropagation @client.on(events.NewMessage) async def _(event): # Will never be reached, because it is the second handler # in the chain. pass Remember to check :ref:`telethon-events-package` if you're looking for the methods reference. __ https://lonamiwebs.github.io/Telethon/types/update.html