Curio is a library of building blocks for performing concurrent I/O and common system programming tasks such as launching subprocesses, working with files, and farming work out to thread and process pools. It uses Python coroutines and the explicit async/await syntax introduced in Python 3.5. Its programming model is based on cooperative multitasking and existing programming abstractions such as threads, sockets, files, subprocesses, locks, and queues. You'll find it to be small, fast, and fun. Curio has no third-party dependencies and does not use the standard asyncio module. Most users will probably find it to be a bit too-low level--it's probably best to think of it as a library for building libraries. Although you might not use it directly, many of its ideas have influenced other libraries with similar functionality.