Unofficial Python 3.6 backports for Debian stretch.
If you just want to grab pre-built Debian packages, you can find them in the
Releases tab on GitHub. Download the ones you want, then run sudo dpkg -i *.deb to install them.
To build from source, clone this repo and run make builddeb on a machine
running Debian stretch. It follows roughly these backporting
instructions in order to build a proper backport of Python
3.6 on stretch.
Building from source is relatively fast and is recommended for anyone who has a healthy distrust of pre-built binaries from a random internet stranger.