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: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!')
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.
.. _asyncio-cli:
You can experiment with an ``asyncio`` concurrent context in the REPL:
.. code-block:: pycon
$ 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'
.. include:: ../includes/wasm-notavail.rst
.. 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-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
.. note::
The source code for asyncio can be found in :source:`Lib/asyncio/`.
|
