internal/tools/: greenlet-3.0.3 metadata and description

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Lightweight in-process concurrent programming

author Alexey Borzenkov
  • Development Status :: 5 - Production/Stable
  • Intended Audience :: Developers
  • License :: OSI Approved :: MIT License
  • Natural Language :: English
  • Programming Language :: C
  • Programming Language :: Python
  • Programming Language :: Python :: 3
  • Programming Language :: Python :: 3 :: Only
  • Programming Language :: Python :: 3.7
  • Programming Language :: Python :: 3.8
  • Programming Language :: Python :: 3.9
  • Programming Language :: Python :: 3.10
  • Programming Language :: Python :: 3.11
  • Programming Language :: Python :: 3.12
  • Operating System :: OS Independent
  • Topic :: Software Development :: Libraries :: Python Modules
description_content_type text/x-rst
keywords greenlet coroutine concurrency threads cooperative
license MIT License
maintainer Jason Madden
  • any
  • Bug Tracker,
  • Source Code,
  • Documentation,
provides_extras test
  • Sphinx ; extra == 'docs'
  • furo ; extra == 'docs'
  • objgraph ; extra == 'test'
  • psutil ; extra == 'test'
requires_python >=3.7
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256 KB
Python Wheel

Greenlets are lightweight coroutines for 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

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

Who is using Greenlet?

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

Getting Greenlet

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

pip install greenlet

Source code archives and binary distributions are available on the python package index at

The source code repository is hosted on github:

Documentation is available on