Celery is a task queue/job queue based on distributed message passing. It is focused on real-time operation, but support scheduling as well.
The execution units, called tasks, are executed concurrently on one or more worker servers. Tasks can execute asynchronously (in the background) or synchronously (wait until ready).
Celery is already used in production to process millions of tasks a day.
Celery was originally created for use with Django, but is now usable from any Python project. It can also operate with other languages via webhooks.
This is a simple task adding two numbers:
from celery.decorators import task
@task
def add(x, y):
    return x + y
You can execute the task in the background, or wait for it to finish:
>>> result = add.delay(8, 8)
>>> result.wait() # wait for and return the result
16
pip install -U celeryThere is a mailing-list available for general discussion.
For those craving real, human interaction, there is also an IRC channel
    (#celery on irc.freenode.net).
Finally, if you find a bug or would like to request a feature, please submit an issue.
This release contains a drastic improvement in reliability and
      performance. Please read the full changelog
      before you upgrade. Download from PyPI,
      or simply install the upgrade using pip install -U celery.
      
This is a bugfix release and has some important changes to the
      shutdown procedure. Also improved compatibility with Windows and Python
      2.4. Read the full Changelog
      for more information. Download from PyPI,
      or simply install the upgrade using pip install -U celery.
      
Celery 1.0 has finally been released! It is available on PyPI for
      downloading. You can also install it via pip install
          celery. You can read the announcement here.
      
1.0 is scheduled to be released this week! Please help us test the latest release candiate to make this happen. To upgrade from an earlier version, please read the changelog.
We finally got a home page. Big thanks to Jan Henrik Helmers