trio-asyncio: A re-implementation of the asyncio mainloop on top of Trio

trio-asyncio is the library of choice for a Python program that contains both Trio and asyncio code.

Trio has native concepts of tasks and task cancellation. Asyncio is based on callbacks and chaining Futures, albeit with nicer syntax, which make handling of failures and timeouts fundamentally less reliable, especially in larger programs. Thus, you really want to use Trio in your project.

On the other hand, there are quite a few robust libraries that have been implemented using asyncio, while Trio’s ecosystem is relatively younger. You really don’t want to re-invent any wheels in your project.

Thus, being able to use asyncio libraries from Trio is useful. trio-asyncio enables you to do that, and more.

With trio-asyncio, you can:

  • Incrementally convert an asyncio application to Trio. Start with a Trio mainloop, call your existing asyncio code, then successively convert procedures to Trio calling conventions.

  • Use any asyncio-capable library in a Trio application.

  • Use trio-asyncio as a building block for convincing other async-ish libraries (Twisted, Promise, …) to be compatible with Trio.

trio-asyncio is tested against the complete asyncio test suite as shipped with each supported version of Python, although a small number of tests fail due to our limited support for starting and stopping the same event loop multiple times. It has also passed the test suite of some complex asyncio libraries such as home-assistant.


trio-asyncio is most useful for applications: it works best when you control the code that starts the event loop (such as the call to If you’re writing a library and want to adopt a Trio-ish worldview without sacrificing asyncio compatibility, you might find anyio helpful.

Helpful facts:

  • Supported environments: Linux, MacOS, or Windows running some kind of Python 3.7-or-better (either CPython or PyPy3 is fine). *BSD and illumOS likely work too, but are untested.

  • Install: python3 -m pip install -U trio-asyncio (or on Windows, maybe py -3 -m pip install -U trio-asyncio). No compiler needed.

  • Tutorial and reference manual:

  • Bug tracker and source code:

Inherited from Trio:

trio-asyncio manual

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