:mod:asyncio --- Asynchronous I/O

.. module:: asyncio :synopsis: Asynchronous I/O.

.. sidebar:: Hello World!

::

   import asyncio

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

   # Python 3.7+
   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 :meth:networking <loop.create_server>, running :meth:subprocesses <loop.subprocess_exec>, handling :meth: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.

.. We use the "rubric" directive here to avoid creating the "Reference" subsection in the TOC.

.. rubric:: Reference

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

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

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

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