i3's interprocess communication (or ipc) is the interface
i3wm uses to receive commands from client applications such
as i3-msg. It also features a publish/subscribe mechanism for
notifying interested parties of window manager events.

i3ipc-python is a Python library for controlling the window
manager. This project is intended to be useful for general
scripting, and for applications that interact with the window
manager like status line generators, notification daemons,
and window pagers.