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".

A "greenlet", on the other hand, is a still more primitive notion of
micro- thread with no implicit scheduling; coroutines, in other words.
This is useful when you want to control exactly when your code runs. You
can build custom scheduled micro-threads on top of greenlet; however, it
seems that greenlets are useful on their own as a way to make advanced
control flow structures. For example, we can recreate generators; the
difference with Python's own generators is that our generators can call
nested functions and the nested functions can yield values too.
Additionally, you don't need a "yield" keyword. See the example in
tests/test_generator.py.

Greenlets are provided as a C extension module for the regular
unmodified interpreter.

1. build dependencies:
   1. python3-module-setuptools
   2. rpm-build-intro >= 2.2.5
   3. rpm-build-python3
   4. gcc-c++