.. _working-with-updates:

====================
Working with Updates
====================

.. contents::


The library can run in four distinguishable modes:

- With no extra threads at all.
- With an extra thread that receives everything as soon as possible (default).
- With several worker threads that run your update handlers.
- A mix of the above.

Since this section is about updates, we'll describe the simplest way to
work with them.


Using multiple workers
**********************

When you create your client, simply pass a number to the
``update_workers`` parameter:

    ``client = TelegramClient('session', api_id, api_hash, update_workers=4)``

4 workers should suffice for most cases (this is also the default on
`Python Telegram Bot`__). You can set this value to more, or even less
if you need.

The next thing you want to do is to add a method that will be called when
an `Update`__ arrives:

    .. code-block:: python

        def callback(update):
            print('I received', update)

        client.add_update_handler(callback)
        # do more work here, or simply sleep!

That's it! Now let's do something more interesting.
Every time an user talks to use, let's reply to them with the same
text reversed:

    .. code-block:: python

        from telethon.tl.types import UpdateShortMessage, PeerUser

        def replier(update):
            if isinstance(update, UpdateShortMessage) and not update.out:
                client.send_message(PeerUser(update.user_id), update.message[::-1])


        client.add_update_handler(replier)
        input('Press enter to stop this!')
        client.disconnect()

We only ask you one thing: don't keep this running for too long, or your
contacts will go mad.


Spawning no worker at all
*************************

All the workers do is loop forever and poll updates from a queue that is
filled from the ``ReadThread``, responsible for reading every item off
the network. If you only need a worker and the ``MainThread`` would be
doing no other job, this is the preferred way. You can easily do the same
as the workers like so:

    .. code-block:: python

        while True:
            try:
                update = client.updates.poll()
                if not update:
                    continue

                print('I received', update)
            except KeyboardInterrupt:
                break

        client.disconnect()

Note that ``poll`` accepts a ``timeout=`` parameter, and it will return
``None`` if other thread got the update before you could or if the timeout
expired, so it's important to check ``if not update``.

This can coexist with the rest of ``N`` workers, or you can set it to ``0``
additional workers:

    ``client = TelegramClient('session', api_id, api_hash, update_workers=0)``

You **must** set it to ``0`` (or other number), as it defaults to ``None``
and there is a different. ``None`` workers means updates won't be processed
*at all*, so you must set it to some value (``0`` or greater) if you want
``client.updates.poll()`` to work.


Using the main thread instead the ``ReadThread``
************************************************

If you have no work to do on the ``MainThread`` and you were planning to have
a ``while True: sleep(1)``, don't do that. Instead, don't spawn the secondary
``ReadThread`` at all like so:

    .. code-block:: python

        client = TelegramClient(
            ...
            spawn_read_thread=False
        )

And then ``.idle()`` from the ``MainThread``:

    ``client.idle()``

You can stop it with :kbd:`Control+C`, and you can configure the signals
to be used in a similar fashion to `Python Telegram Bot`__.

As a complete example:

    .. code-block:: python

        def callback(update):
            print('I received', update)

        client = TelegramClient('session', api_id, api_hash,
                                update_workers=1, spawn_read_thread=False)

        client.connect()
        client.add_update_handler(callback)
        client.idle()  # ends with Ctrl+C
        client.disconnect()


__ https://python-telegram-bot.org/
__ https://lonamiwebs.github.io/Telethon/types/update.html
__ https://github.com/python-telegram-bot/python-telegram-bot/blob/4b3315db6feebafb94edcaa803df52bb49999ced/telegram/ext/updater.py#L460