.. _sessions:

==============
Session Files
==============

The first parameter you pass to the constructor of the ``TelegramClient`` is
the ``session``, and defaults to be the session name (or full path). That is,
if you create a ``TelegramClient('anon')`` instance and connect, an
``anon.session`` file will be created on the working directory.

These database files using ``sqlite3`` contain the required information to
talk to the Telegram servers, such as to which IP the client should connect,
port, authorization key so that messages can be encrypted, and so on.

These files will by default also save all the input entities that you've seen,
so that you can get information about an user or channel by just their ID.
Telegram will **not** send their ``access_hash`` required to retrieve more
information about them, if it thinks you have already seem them. For this
reason, the library needs to store this information offline.

The library will by default too save all the entities (chats and channels
with their name and username, and users with the phone too) in the session
file, so that you can quickly access them by username or phone number.

If you're not going to work with updates, or don't need to cache the
``access_hash`` associated with the entities' ID, you can disable this
by setting ``client.session.save_entities = False``, or pass it as a
parameter to the ``TelegramClient``.

If you don't want to save the files as a database, you can also create
your custom ``Session`` subclass and override the ``.save()`` and ``.load()``
methods. For example, you could save it on a database:

    .. code-block:: python

        class DatabaseSession(Session):
            def save():
                # serialize relevant data to the database

            def load():
                # load relevant data to the database


You should read the ````session.py```` source file to know what "relevant
data" you need to keep track of.