`!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 <coroutine> concurrently and have full control over their execution;
• perform network IO and IPC <asyncio-streams>;
• control subprocesses <asyncio-subprocess>;
• distribute tasks via queues <asyncio-queues>;
• synchronize <asyncio-sync> concurrent code;

For introspection, asyncio provides APIs and tools for:

• inspecting the async call graph <asyncio-graph> of tasks and futures;
• inspecting tasks in another running Python process with command-line tools <asyncio-introspection-tools>;

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

• create and manage event loops <asyncio-event-loop>, which provide asynchronous APIs for networking <loop_create_server>, running subprocesses <loop_subprocess_exec>, handling OS signals <loop_add_signal_handler>, etc;
• implement efficient protocols using transports <asyncio-transports-protocols>;
• bridge <asyncio-futures> 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'

This REPL provides limited compatibility with PYTHON_BASIC_REPL. It is recommended that the default REPL is used for full functionality and the latest features.

Reference

[!NOTE] The source code for asyncio can be found in Lib/asyncio/.