zloop¶

An asyncio event loop with a Zig core! ⚡

Source Code: https://github.com/Kludex/zloop

zloop is an asyncio event loop whose engine is written in Zig. It is to asyncio what uvloop is: a drop-in replacement for the default event loop that you can use without changing your application code.

The difference is what's underneath. uvloop wraps libuv from Cython; zloop is a hand-written reactor in Zig - kqueue/epoll, plus an opt-in io_uring backend on Linux - bound to CPython through a thin adapter.

The key features are:

• Drop-in: it's a normal asyncio.AbstractEventLoop. For the common server/client workloads - TCP, TLS, Unix sockets, the streams and transport APIs - your code runs unchanged. (A few rarely-used loop APIs aren't implemented yet; see Compatibility.)
• Fast: the hot paths - scheduling, timers, and socket I/O - run in Zig, not Python. See Performance for benchmarks against asyncio and uvloop.
• Familiar: works the same way uvloop does, so the tools you already know (uvicorn, AnyIO, FastAPI) just pick it up.
• Tested: it passes uvicorn's entire test suite, plus its own suite at 100% coverage.

Installation¶

$ pip install zloop

Example¶

Let's create the simplest possible thing: run a coroutine on zloop.

import asyncio

import zloop


async def main():
    print("Hello from a Zig event loop 👋")


asyncio.run(main(), loop_factory=zloop.new_event_loop)  # (1)!

1. This is the one line that matters. loop_factory tells asyncio.run() which loop to build - and zloop.new_event_loop builds a zloop one.

   Everything else is plain asyncio. That's the whole point.

Run it:

$ python main.py

Hello from a Zig event loop 👋

That's it. The coroutine ran, but the loop driving it - the timers, the callback scheduling, the I/O polling - was all Zig. 🎉

Where to go next¶