Compatibility and Convenience¶
Telethon is an asyncio
library. Compatibility is an important concern,
and while it can’t always be kept and mistakes happens, the Changelog (Version History)
is there to tell you when these important changes happen.
Compatibility¶
Some decisions when developing will inevitable be proven wrong in the future.
One of these decisions was using threads. Now that Python 3.4 is reaching EOL
and using asyncio
is usable as of Python 3.5 it makes sense for a library
like Telethon to make a good use of it.
If you have old code, just use old versions of the library! There is
nothing wrong with that other than not getting new updates or fixes, but
using a fixed version with pip install telethon==0.19.1.6
is easy
enough to do.
You might want to consider using Virtual Environments in your projects.
There’s no point in maintaining a synchronous version because the whole point is that people don’t have time to upgrade, and there has been several changes and clean-ups. Using an older version is the right way to go.
Sometimes, other small decisions are made. These all will be reflected in the Changelog (Version History) which you should read when upgrading.
If you want to jump the asyncio
boat, here are some of the things you will
need to start migrating really old code:
# 1. Import the client from telethon.sync
from telethon.sync import TelegramClient
# 2. Change this monster...
try:
assert client.connect()
if not client.is_user_authorized():
client.send_code_request(phone_number)
me = client.sign_in(phone_number, input('Enter code: '))
... # REST OF YOUR CODE
finally:
client.disconnect()
# ...for this:
with client:
... # REST OF YOUR CODE
# 3. client.idle() no longer exists.
# Change this...
client.idle()
# ...to this:
client.run_until_disconnected()
# 4. client.add_update_handler no longer exists.
# Change this...
client.add_update_handler(handler)
# ...to this:
client.add_event_handler(handler)
In addition, all the update handlers must be async def
, and you need
to await
method calls that rely on network requests, such as getting
the chat or sender. If you don’t use updates, you’re done!
Convenience¶
Note
The entire documentation assumes you have done one of the following:
from telethon import TelegramClient, sync
# or
from telethon.sync import TelegramClient
This makes the examples shorter and easier to think about.
For quick scripts that don’t need updates, it’s a lot more convenient to
forget about asyncio
and just work with sequential code. This can prove
to be a powerful hybrid for running under the Python REPL too.
from telethon.sync import TelegramClient
# ^~~~~ note this part; it will manage the asyncio loop for you
with TelegramClient(...) as client:
print(client.get_me().username)
# ^ notice the lack of await, or loop.run_until_complete().
# Since there is no loop running, this is done behind the scenes.
#
message = client.send_message('me', 'Hi!')
import time
time.sleep(5)
message.delete()
# You can also have an hybrid between a synchronous
# part and asynchronous event handlers.
#
from telethon import events
@client.on(events.NewMessage(pattern='(?i)hi|hello'))
async def handler(event):
await event.reply('hey')
client.run_until_disconnected()
Some methods, such as with
, start
, disconnect
and
run_until_disconnected
work both in synchronous and asynchronous
contexts by default for convenience, and to avoid the little overhead
it has when using methods like sending a message, getting messages, etc.
This keeps the best of both worlds as a sane default.
Note
As a rule of thumb, if you’re inside an async def
and you need
the client, you need to await
calls to the API. If you call other
functions that also need API calls, make them async def
and await
them too. Otherwise, there is no need to do so with this mode.
Speed¶
When you’re ready to micro-optimize your application, or if you simply
don’t need to call any non-basic methods from a synchronous context,
just get rid of telethon.sync
and work inside an async def
:
import asyncio
from telethon import TelegramClient, events
async def main():
async with TelegramClient(...) as client:
print((await client.get_me()).username)
# ^_____________________^ notice these parenthesis
# You want to ``await`` the call, not the username.
#
message = await client.send_message('me', 'Hi!')
await asyncio.sleep(5)
await message.delete()
@client.on(events.NewMessage(pattern='(?i)hi|hello'))
async def handler(event):
await event.reply('hey')
await client.run_until_disconnected()
asyncio.run(main())
The telethon.sync
magic module essentially wraps every method behind:
asyncio.run(main())
With some other tricks, so that you don’t have to write it yourself every time. That’s the overhead you pay if you import it, and what you save if you don’t.
Learning¶
You know the library uses asyncio
everywhere, and you want to learn
how to do things right. Even though asyncio
is its own topic, the
documentation wants you to learn how to use Telethon correctly, and for
that, you need to use asyncio
correctly too. For this reason, there
is a section called Mastering asyncio that will introduce you to
the asyncio
world, with links to more resources for learning how to
use it. Feel free to check that section out once you have read the rest.