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.

Greenlets are lightweight coroutines for in-process concurrent
programming.

Who is using Greenlet?
======================

There are several libraries that use Greenlet as a more flexible
alternative to Python's built in coroutine support:

 - `Concurrence`_
 - `Eventlet`_
 - `Gevent`_

.. _Concurrence: http://opensource.hyves.org/concurrence/
.. _Eventlet: http://eventlet.net/
.. _Gevent: http://www.gevent.org/

Getting Greenlet
================

The easiest way to get Greenlet is to install it with pip or
easy_install::

  pip install greenlet
  easy_install greenlet


Source code archives and windows installers are available on the
python package index at http://pypi.python.org/pypi/greenlet

The source code repository is hosted on github:
https://github.com/python-greenlet/greenlet

The master branch - i.e. the `development version`_ - can be installed
directly by running one of the following::

  pip install greenlet==dev
  easy_install greenlet==dev

.. _`development version`: https://github.com/python-greenlet/greenlet/zipball/master#egg=greenlet-dev
