Trollius is deprecated


The Trollius project is now deprecated!

Trollius is deprecated since the release 2.1. The maintainer of Trollius, Victor Stinner, doesn’t want to maintain the project anymore for many reasons. This page lists some reasons.

DON’T PANIC! There is the asyncio project which has the same API and is well maintained! Only trollius is deprecated.

Since the Trollius is used for some projects in the wild, Trollius will not disappear. You can only expect minimum maintenance like minor bugfixes. Don’t expect new features nor synchronization with the latest asyncio.

To be clear: I am looking for a new maintainer. If you want to take over trollius: please do it, I will give you everything you need (and maybe more!).


asyncio is here! asyncio is well maintainted, has a growing community, has many libraries and don’t stop evolving to be enhanced by users feedbacks. I (Victor Stinner) even heard that it is fast!

asyncio requires Python 3.3 or newer. Yeah, you all have a long list of reasons to not port your legacy code for Python 3. But I have my own reasons to prefer to invest in the Python 3 rather than in legacy Python (Python 2).

No Trollius Community

  • Very the asyncio is growing everyday, there is no trollius community. Sadly, asyncio libraries don’t work for trollius.
  • Only very few libraries support Trollius: to be clear, there is no HTTP client for Trollius, whereas HTTP is the most common protocol in 2015.
  • It’s a deliberate choice of library authors to not support Trollius to keep a simple code base. The Python 3 is simpler than Python 2: supporting Python 2 in a library requires more work. For example, aiohttp doesn’t want to support trollius.

Python 2

  • Seriously? Come on! Stop procrastination and upgrade your code to Python 3!

Lack of interest

  • The Trollius project was created to replace eventlet with asyncio (trollius) in the OpenStack project, but replacing eventlet with trollius has failed for different reasons. The original motivation is gone.

Technical issues with trollius

  • While Trollius API is “simple”, the implementation is very complex to be efficient on all platforms.
  • Trollius requires backports of libraries to support old Python versions. These backports are not as well supported as the version in the Python standard library.
  • Supporting Python 2.7, Python 3.3 and Python 3.5 in the same code base and supporting asyncio is very difficult. Generators and coroutines changed a lot in each Python version. For example, hacks are required to support Python 3.5 with the PEP 479 which changed the usage of the StopIteration exception. Trollius initially also supported Python 2.6 and 3.2.

Other technical issues

  • Building wheel packages on Windows is difficult (need a running Windows, need working Windows SDKs for each version of Python, need to test and fix bugs specific to Windows, etc.)