greenlet 0.3

Lightweight in-process concurrent programming

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 in-process concurrent programming. This package is the py.magic.greenlet module from the py lib.

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

Getting Greenlet

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

pip install greenlet
easy_install greenlet