uvloop is a fast, drop-in replacement of the built-in asyncio event loop. uvloop is released under the MIT license.

uvloop and asyncio, combined with the power of async/await in Python 3.5, makes it easier than ever to write high-performance networking code in Python.

uvloop makes asyncio fast. In fact, it is at least 2x faster than nodejs, gevent, as well as any other Python asynchronous framework. The performance of uvloop-based asyncio is close to that of Go programs.

You can read more about uvloop in this blog post.


The asyncio module, introduced by PEP 3156, is a collection of network transports, protocols, and streams abstractions, with a pluggable event loop. The event loop is the heart of asyncio. It provides APIs for:

  • scheduling calls,
  • transmitting data over the network,
  • performing DNS queries,
  • handling OS signals,
  • convenient abstractions to create servers and connections,
  • working with subprocesses asynchronously.

uvloop implements the asyncio.AbstractEventLoop interface which means that it provides a drop-in replacement of the asyncio event loop.

uvloop is written in Cython and is built on top of libuv.

libuv is a high performance, multiplatform asynchronous I/O library used by nodejs. Because of how wide-spread and popular nodejs is, libuv is fast and stable.

uvloop implements all asyncio event loop APIs. High-level Python objects wrap low-level libuv structs and functions. Inheritance is used to keep the code DRY and ensure that any manual memory management is in sync with libuv primitives’ lifespans.