Eventlet Documentation


New usages of eventlet are now heavily discouraged! Please read the following.

Eventlet was created almost 18 years ago, at a time where async features were absent from the CPython stdlib. With time eventlet evolved and CPython too, but since several years the maintenance activity of eventlet decreased leading to a growing gap between eventlet and the CPython implementation.

This gap is now too high and can lead you to unexpected side effects and bugs in your applications.

Eventlet now follows a new maintenance policy. Only maintenance for stability and bug fixing will be provided. No new features will be accepted, except those related to the asyncio migration. Usages in new projects are discouraged. Our goal is to plan the retirement of eventlet and to give you ways to move away from eventlet.

If you are looking for a library to manage async network programming, and if you do not yet use eventlet, then, we encourage you to use asyncio, which is the official async library of the CPython stdlib.

If you already use eventlet, we hope to enable migration to asyncio for some use cases; see Migrating off of Eventlet. Only new features related to the migration solution will be accepted.

If you have questions concerning maintenance goals or concerning the migration do not hesitate to open a new issue, we will be happy to answer them.


The easiest way to get Eventlet is to use pip:

pip install -U eventlet

To install latest development version once:

pip install -U https://github.com/eventlet/eventlet/archive/master.zip


Code talks! This is a simple web crawler that fetches a bunch of urls concurrently:

urls = [

import eventlet
from eventlet.green.urllib.request import urlopen

def fetch(url):
    return urlopen(url).read()

pool = eventlet.GreenPool()
for body in pool.imap(fetch, urls):
    print("got body", len(body))

Supported Python Versions

Currently supporting CPython 3.7+.

Concepts & References

Want to contribute?


Eventlet is made available under the terms of the open source MIT license


For further details about released versions of Eventlet please take a look at the changelog.

Authors & History

You have questions or you may have find a bug and you want to contact authors or maintainers, then please take a look at Authors.

You want to learn more about the history of Eventlet, then, please take a look at History.

Indices and tables