.. module:: asyncio
   :synopsis: 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:

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

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

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

Reference

.. toctree::
   :caption: High-level APIs
   :maxdepth: 1

   asyncio-runner.rst
   asyncio-task.rst
   asyncio-stream.rst
   asyncio-sync.rst
   asyncio-subprocess.rst
   asyncio-queue.rst
   asyncio-exceptions.rst

.. toctree::
   :caption: Low-level APIs
   :maxdepth: 1

   asyncio-eventloop.rst
   asyncio-future.rst
   asyncio-protocol.rst
   asyncio-policy.rst
   asyncio-platforms.rst
   asyncio-extending.rst

.. toctree::
   :caption: Guides and Tutorials
   :maxdepth: 1

   asyncio-api-index.rst
   asyncio-llapi-index.rst
   asyncio-dev.rst