Telethon Optional Dependencies

If cryptg is installed, the library will work a lot faster, since encryption and decryption will be made in C instead of Python. If your code deals with a lot of updates or you are downloading/uploading a lot of files, you will notice a considerable speed-up (from a hundred kilobytes per second to several megabytes per second, if your connection allows it). If it’s not installed, pyaes will be used (which is pure Python, so it’s much slower).

If pillow is installed, large images will be automatically resized when sending photos to prevent Telegram from failing with “invalid image”. Official clients also do this.

If aiohttp is installed, the library will be able to download WebDocument media files (otherwise you will get an error).

If hachoir is installed, it will be used to extract metadata from files when sending documents. Telegram uses this information to show the song’s performer, artist, title, duration, and for videos too (including size). Otherwise, they will default to empty values, and you can set the attributes manually.

Note

Some of the modules may require additional dependencies before being installed through pip. If you have an apt-based system, consider installing the most commonly missing dependencies (with the right pip):

apt update
apt install clang lib{jpeg-turbo,webp}-dev python{,-dev} zlib-dev
pip install -U --user setuptools
pip install -U --user telethon cryptg pillow

Thanks to @bb010g for writing down this nice list.