Telethon
========
.. epigraph::

  ⭐️ Thanks **everyone** who has starred the project, it means a lot!

**Telethon** is Telegram client implementation in **Python** which uses the latest available API of Telegram.

Before opening an issue about how to use the library, **please** make sure you have read and followed
the steps mentioned under `Using Telethon`_ and are using the latest version! A lot of people ask simple
questions which will only be answered as "please see the ``README.rst``". And you should use the search
before posting an issue, too.

If you come here often, you may want to go to the `docs <https://lonamiwebs.github.io/Telethon>`_.

.. contents:: Table of contents

Why Telethon?
=============
.. epigraph::

  Why should I bother with Telethon? There are more mature projects already, such as
  `telegram-cli <https://github.com/vysheng/tg>`_ with even (limited) Python support. And we have the
  `official <https://github.com/telegramdesktop/tdesktop>`_ `clients <https://github.com/DrKLO/Telegram>`_!

With Telethon you don't really need to know anything before using it. Create a client with your settings.
Connect. You're ready to go.

Being written **entirely** on Python, Telethon can run as a script under any environment you wish, (yes,
`Android too <https://f-droid.org/repository/browse/?fdfilter=termux&fdid=com.termux>`_). You can schedule it,
or use it in any other script you have. Want to send a message to someone when you're available? Write a script.
Do you want check for new messages at a given time and find relevant ones? Write a script.

Hungry for more API calls which the ``TelegramClient`` class doesn't *seem* to have implemented?
Please read `Using more than just TelegramClient`_.

Obtaining your Telegram ``API ID`` and ``Hash``
===============================================
In order to use Telethon, you first need to obtain your very own API ID and Hash:

1. Follow `this link <https://my.telegram.org>`_ and login with your phone number.
2. Click under *API Development tools*.
3. A *Create new application* window will appear. Fill in your application details.
   There is no need to enter any *URL*, and only the first two fields (*App title* and *Short name*)
   can be changed later as long as I'm aware.
4. Click on *Create application* at the end.

Now that you know your ``API ID`` and ``Hash``, you can continue installing Telethon.

Installing Telethon
===================

Installing Telethon via ``pip``
-------------------------------
On a terminal, issue the following command:

.. code:: sh

  sudo -H pip install telethon

If you get something like "SyntaxError: invalid syntax" on the ``from error``
line, it's because ``pip`` defaults to Python 2. Use `pip3` instead.

If you already have Telethon installed,
upgrade with ``pip install --upgrade telethon``!

Installing Telethon manually
----------------------------

1. Install the required ``pyaes`` module: ``sudo -H pip install pyaes``
   (`GitHub <https://github.com/ricmoo/pyaes>`_, `package index <https://pypi.python.org/pypi/pyaes>`_)
2. Clone Telethon's GitHub repository: ``git clone https://github.com/LonamiWebs/Telethon.git``
3. Enter the cloned repository: ``cd Telethon``
4. Run the code generator: ``python3 setup.py gen_tl``
5. Done!

Running Telethon
================
If you've installed Telethon via pip, launch an interactive python3 session and enter the following:

.. code:: python

  >>> from telethon import TelegramClient
  >>> api_id = 12345
  >>> api_hash = '0123456789abcdef0123456789abcdef'
  >>> # 'session_id' can be 'your_name'. It'll be saved as your_name.session
  ... client = TelegramClient('session_id', api_id, api_hash)
  >>> client.connect()
  True
  >>>
  >>> if not client.is_user_authorized():
  >>>   client.send_code_request('+34600000000')
  >>>   client.sign_in('+34600000000', input('Enter code: '))
  ...
  >>> # Now you can use the connected client as you wish
  >>> dialogs, entities = client.get_dialogs(10)
  >>> print('\n'.join('{}. {}'.format(i, str(e))
  ...                 for i, e in enumerate(entities)))

If, on the other hand, you've installed Telethon manually, head to the ``api/`` directory and create a
copy of the ``settings_example`` file, naming it ``settings`` (lowercase!). Then fill the file with the
corresponding values (your ``api_id``, ``api_hash`` and phone number in international format).

Then, simply run ``./try_telethon.py`` to start the interactive example.

.. _Using Telethon:

Using Telethon
==============
If you really want to learn how to use Telethon, it is **highly advised** that
you take a look to the
`InteractiveTelegramClient <https://github.com/LonamiWebs/Telethon/blob/master/telethon_examples/interactive_telegram_client.py>`_
file and check how it works. This file contains everything you'll need to
build your own application, since it shows, among other things:

1. Authorizing the user for the first time.
2. Support to enter the 2-steps-verification code.
3. Retrieving dialogs (chats) and the messages history.
4. Sending messages and files.
5. Downloading files.
6. Updates thread.

If you want a nicer way to see all the available requests and types at your
disposal, please check the
`official Telethon documentation <https://lonamiwebs.github.io/Telethon>`_.
There you'll find a list of all the methods, types and available constructors.

More examples are also available under the ``telethon_examples/`` folder.

If you're using Telethon under ARM, you may want to install ``sympy`` through
``pip`` for a substantial speed-up when generating the keys required to
connect to Telegram (you can of course do this on desktop too). See
`issue #199 <https://github.com/LonamiWebs/Telethon/issues/199>`_ for more.

Common errors
-------------

Errors resulting from Telegram queries all subclass the ``RPCError`` class.
This class is further specialized into further errors:

* ``InvalidDCError`` (303), the request must be repeated on another DC.
* ``BadRequestError`` (400), the request contained errors.
* ``UnauthorizedError`` (401), the user is not authorized yet.
* ``ForbiddenError`` (403), privacy violation error.
* ``NotFoundError`` (404), make sure you're invoking ``Request``'s!
* ``FloodError`` (420), the same request was repeated many times. Must wait ``.seconds``.

Further specialization is also available, for instance, the ``SessionPasswordNeededError``
when signing in means that a password must be provided to continue.

If the error is not recognised, it will only be an ``RPCError``.

Unless you know what you're doing, you should download media by always using the ``.download_file()``
function, which supports a ``str`` or a file handle as parameters. Otherwise, ``.invoke()`` may raise
``InvalidDCError`` which you will have to handle, and in turn call ``.invoke_on_dc()`` manually.

Advanced uses
=============

.. _Using more than just TelegramClient:

Using more than just ``TelegramClient``
---------------------------------------
The ``TelegramClient`` class should be used to provide a quick, well-documented and simplified starting point.
It is **not** meant to be a place for *all* the available Telegram ``Request``'s, because there are simply too many.

However, this doesn't mean that you cannot ``invoke`` all the power of Telegram's API.
Whenever you need to ``call`` a Telegram ``Request``, all you need to do is the following:

.. code:: python

  result = client(SomeRequest(...))

  # Or the old way:
  result = client.invoke(SomeRequest(...))

You have just called ``SomeRequest`` and retrieved its ``result``! That wasn't hard at all, was it?
Now you may wonder, what's the deal with *all the power of Telegram's API*? Have a look under ``tl/functions/``.
That is *everything* you can do. You have **over 200 API** ``Request``'s at your disposal.

However, we don't pretty know *how* that ``result`` looks like. Easy. ``print(str(result))`` should
give you a quick overview. Nevertheless, there may be more than a single ``result``! Let's have a look at
this seemingly innocent ``TL`` definition:

``messages.getWebPagePreview#25223e24 message:string = MessageMedia;``

Focusing on the end, we can see that the ``result`` of invoking ``GetWebPagePreviewRequest`` is ``MessageMedia``.
But how can ``MessageMedia`` exactly look like? It's time to have another look, but this time under ``tl/types/``:

.. code:: sh

  $ tree -P "message_media_*"
  .
  ├── tl
  │   └── types
  │       ├── message_media_contact.py
  │       ├── message_media_document.py
  │       ├── message_media_empty.py
  │       ├── message_media_geo.py
  │       ├── message_media_photo.py
  │       ├── message_media_unsupported.py
  │       ├── message_media_venue.py
  │       └── message_media_web_page.py

Those are *eight* different types! How do we know what exact type it is to determine its properties? A simple
``if type(result) == MessageMediaContact:`` or similar will do. Now you're ready to take advantage of
Telegram's polymorphism.

Tips for porting Telethon
-------------------------
First of all, you need to understand how the ``scheme.tl`` (``TL`` language) works. Every object
definition is written as follows:

``name#id argument_name:argument_type = CommonType``

This means that in a single line you know what the ``TLObject`` name is. You know it's unique ID, and you
know what arguments it has. It really isn't that hard to write a generator for generating code to any platform!

The generated code should also be able to *encode* the ``Request`` into bytes, so they can be sent over
the network. This isn't a big deal either, because you know how the ``TLObject``'s are made.

Once you have your own `code generator <telethon_generator/tl_generator.py>`_, start by looking at the
`first release <https://github.com/LonamiWebs/Telethon/releases/tag/v0.1>`_ of Telethon.
The code there is simple to understand, easy to read and hence easy to port. No extra useless features.
Only the bare bones. Perfect for starting a *new implementation*.

P.S.: I may have lied a bit. The ``TL`` language is not that easy. But it's not that hard either.
You're free to sniff the ``parser/`` files and learn how to parse other more complex lines.
Or simply use that code and change the `SourceBuilder <telethon_generator/parser/source_builder.py>`_!

Notes about the code generator
------------------------------
The code generator will skip the types considered as *core types*. These types are usually included in
almost every programming language, such as boolean values or lists, and also the Telegram True flag,
which is *not* sent but rather used to determine whether that flag should be enabled or not.

Updating the ``scheme.tl``
--------------------------
Have you found a more updated version of the ``scheme.tl`` file? Those are great news! Updating is as simple
as grabbing the
`latest version <https://github.com/telegramdesktop/tdesktop/blob/dev/Telegram/Resources/scheme.tl>`_
and replacing the one you can find in this same directory by the updated one.
Don't forget to run ``python3 setup.py gen_tl``.

If the changes weren't too big, everything should still work the same way as it did before; but with extra features.

Using a proxy
-------------
If you want to use Telethon via proxy, you have to install
`PySocks (via pip or manual) <https://github.com/Anorov/PySocks#installation>`_.
Once this is done, pass the proxy settings to the ``TelegramClient`` constructor:

.. code:: python

  >>> from telethon import TelegramClient
  >>> import socks
  >>> client = TelegramClient('session_id',
  ...     api_id=12345, api_hash='0123456789abcdef0123456789abcdef',
  ...     proxy=(socks.SOCKS5, 'localhost', 4444))

The ``proxy=`` argument should be a tuple, a list or a dict, consisting of parameters described
`here <https://github.com/Anorov/PySocks#usage-1>`_.