asyncio — Asynchronous I/O

import asyncio

async def main():
    print('Hello ...')
    await asyncio.sleep(1)
    print('... World!')

asyncio.run(main())

asyncio is a library to write concurrent code using the async/await syntax.

asyncio is used as a foundation for multiple Python asynchronous frameworks that provide high-performance network and web-servers, database connection libraries, distributed task queues, etc.

asyncio is often a perfect fit for IO-bound and high-level structured network code.

asyncio provides a set of high-level APIs to:

run Python coroutines concurrently and have full control over their execution;
perform network IO and IPC;
control subprocesses;
distribute tasks via queues;
synchronize concurrent code;

Additionally, there are low-level APIs for library and framework developers to:

create and manage event loops, which provide asynchronous APIs for networking, running subprocesses, handling OS signals, etc;
implement efficient protocols using transports;
bridge callback-based libraries and code with async/await syntax.

You can experiment with an asyncio concurrent context in the REPL:

$ python -m asyncio
asyncio REPL ...
Use "await" directly instead of "asyncio.run()".
Type "help", "copyright", "credits" or "license" for more information.
>>> import asyncio
>>> await asyncio.sleep(10, result='hello')
'hello'

Availability: not Emscripten, not WASI.

This module does not work or is not available on WebAssembly platforms wasm32-emscripten and wasm32-wasi. See WebAssembly platforms for more information.

Reference

High-level APIs

Low-level APIs

Guides and Tutorials

Note

The source code for asyncio can be found in Lib/asyncio/.