mirror of
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230 lines
7.3 KiB
ReStructuredText
230 lines
7.3 KiB
ReStructuredText
================
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Updates in Depth
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================
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Properties vs. Methods
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======================
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The event shown above acts just like a `custom.Message
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<telethon.tl.custom.message.Message>`, which means you
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can access all the properties it has, like ``.sender``.
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**However** events are different to other methods in the client, like
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`client.get_messages <telethon.client.messages.MessageMethods.get_messages>`.
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Events *may not* send information about the sender or chat, which means it
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can be `None`, but all the methods defined in the client always have this
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information so it doesn't need to be re-fetched. For this reason, you have
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``get_`` methods, which will make a network call if necessary.
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In short, you should do this:
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.. code-block:: python
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@client.on(events.NewMessage)
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async def handler(event):
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# event.input_chat may be None, use event.get_input_chat()
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chat = await event.get_input_chat()
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sender = await event.get_sender()
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buttons = await event.get_buttons()
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async def main():
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async for message in client.get_messages('me', 10):
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# Methods from the client always have these properties ready
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chat = message.input_chat
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sender = message.sender
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buttons = message.buttons
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Notice, properties (`message.sender
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<telethon.tl.custom.message.Message.sender>`) don't need an ``await``, but
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methods (`message.get_sender
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<telethon.tl.custom.message.Message.get_sender>`) **do** need an ``await``,
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and you should use methods in events for these properties that may need network.
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Events Without the client
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=========================
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The code of your application starts getting big, so you decide to
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separate the handlers into different files. But how can you access
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the client from these files? You don't need to! Just `events.register
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<telethon.events.register>` them:
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.. code-block:: python
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# handlers/welcome.py
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from telethon import events
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@events.register(events.NewMessage('(?i)hello'))
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async def handler(event):
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client = event.client
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await event.respond('Hey!')
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await client.send_message('me', 'I said hello to someone')
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Registering events is a way of saying "this method is an event handler".
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You can use `telethon.events.is_handler` to check if any method is a handler.
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You can think of them as a different approach to Flask's blueprints.
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It's important to note that this does **not** add the handler to any client!
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You never specified the client on which the handler should be used. You only
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declared that it is a handler, and its type.
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To actually use the handler, you need to `client.add_event_handler
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<telethon.client.updates.UpdateMethods.add_event_handler>` to the
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client (or clients) where they should be added to:
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.. code-block:: python
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# main.py
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from telethon import TelegramClient
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import handlers.welcome
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with TelegramClient(...) as client:
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client.add_event_handler(handlers.welcome.handler)
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client.run_until_disconnected()
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This also means that you can register an event handler once and
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then add it to many clients without re-declaring the event.
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Events Without Decorators
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=========================
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If for any reason you don't want to use `telethon.events.register`,
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you can explicitly pass the event handler to use to the mentioned
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`client.add_event_handler
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<telethon.client.updates.UpdateMethods.add_event_handler>`:
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.. code-block:: python
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from telethon import TelegramClient, events
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async def handler(event):
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...
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with TelegramClient(...) as client:
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client.add_event_handler(handler, events.NewMessage)
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client.run_until_disconnected()
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Similarly, you also have `client.remove_event_handler
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<telethon.client.updates.UpdateMethods.remove_event_handler>`
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and `client.list_event_handlers
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<telethon.client.updates.UpdateMethods.list_event_handlers>`.
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The ``event`` argument is optional in all three methods and defaults to
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`events.Raw <telethon.events.raw.Raw>` for adding, and `None` when
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removing (so all callbacks would be removed).
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.. note::
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The ``event`` type is ignored in `client.add_event_handler
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<telethon.client.updates.UpdateMethods.add_event_handler>`
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if you have used `telethon.events.register` on the ``callback``
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before, since that's the point of using such method at all.
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Stopping Propagation of Updates
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===============================
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There might be cases when an event handler is supposed to be used solitary and
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it makes no sense to process any other handlers in the chain. For this case,
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it is possible to raise a `telethon.events.StopPropagation` exception which
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will cause the propagation of the update through your handlers to stop:
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.. code-block:: python
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from telethon.events import StopPropagation
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@client.on(events.NewMessage)
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async def _(event):
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# ... some conditions
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await event.delete()
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# Other handlers won't have an event to work with
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raise StopPropagation
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@client.on(events.NewMessage)
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async def _(event):
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# Will never be reached, because it is the second handler
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# in the chain.
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pass
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Remember to check :ref:`telethon-events` if you're looking for
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the methods reference.
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Understanding asyncio
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=====================
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With `asyncio`, the library has several tasks running in the background.
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One task is used for sending requests, another task is used to receive them,
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and a third one is used to handle updates.
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To handle updates, you must keep your script running. You can do this in
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several ways. For instance, if you are *not* running `asyncio`'s event
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loop, you should use `client.run_until_disconnected
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<telethon.client.updates.UpdateMethods.run_until_disconnected>`:
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.. code-block:: python
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import asyncio
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from telethon import TelegramClient
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client = TelegramClient(...)
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...
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client.run_until_disconnected()
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Behind the scenes, this method is ``await``'ing on the `client.disconnected
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<telethon.client.telegrambaseclient.TelegramBaseClient.disconnected>` property,
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so the code above and the following are equivalent:
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.. code-block:: python
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import asyncio
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from telethon import TelegramClient
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client = TelegramClient(...)
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async def main():
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await client.disconnected
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loop = asyncio.get_event_loop()
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loop.run_until_complete(main())
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You could also run `client.disconnected
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<telethon.client.telegrambaseclient.TelegramBaseClient.disconnected>`
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until it completed.
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But if you don't want to ``await``, then you should know what you want
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to be doing instead! What matters is that you shouldn't let your script
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die. If you don't care about updates, you don't need any of this.
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Notice that unlike `client.disconnected
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<telethon.client.telegrambaseclient.TelegramBaseClient.disconnected>`,
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`client.run_until_disconnected
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<telethon.client.updates.UpdateMethods.run_until_disconnected>` will
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handle ``KeyboardInterrupt`` with you. This method is special and can
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also be ran while the loop is running, so you can do this:
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.. code-block:: python
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async def main():
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await client.run_until_disconnected()
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loop.run_until_complete(main())
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Sequential Updates
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==================
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If you need to process updates sequentially (i.e. not in parallel),
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you should set ``sequential_updates=True`` when creating the client:
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.. code-block:: python
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with TelegramClient(..., sequential_updates=True) as client:
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...
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