The greenlet package is a spin-off of stackless, a version of cpython that supports micro-threads called "tasklets". tasklets run pseudo-concurrently (typically in a single or a few os-level threads) and are synchronized with data exchanges on "channels".

greenlet is the standalone package derived from the py lib, and is used by several non-blocking io packages as a more flexible alternative to python's built in coroutines.

this is the development package for greenlet.