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The basics
==========
.. py:currentmodule:: anyio
AnyIO requires Python 3.8 or later to run. It is recommended that you set up a
virtualenv_ when developing or playing around with AnyIO.
Installation
------------
To install AnyIO, run:
.. code-block:: bash
pip install anyio
To install a supported version of Trio_, you can install it as an extra like this:
.. code-block:: bash
pip install anyio[trio]
Running async programs
----------------------
The simplest possible AnyIO program looks like this::
from anyio import run
async def main():
print('Hello, world!')
run(main)
This will run the program above on the default backend (asyncio). To run it on another
supported backend, say Trio_, you can use the ``backend`` argument, like so::
run(main, backend='trio')
But AnyIO code is not required to be run via :func:`run`. You can just as well use the
native ``run()`` function of the backend library::
import sniffio
import trio
from anyio import sleep
async def main():
print('Hello')
await sleep(1)
print("I'm running on", sniffio.current_async_library())
trio.run(main)
.. versionchanged:: 4.0.0
On the ``asyncio`` backend, ``anyio.run()`` now uses a back-ported version of
:class:`asyncio.Runner` on Pythons older than 3.11.
.. _backend options:
Backend specific options
------------------------
**Asyncio**:
* options covered in the documentation of :class:`asyncio.Runner`
* ``use_uvloop`` (``bool``, default=False): Use the faster uvloop_ event loop
implementation, if available (this is a shorthand for passing
``loop_factory=uvloop.new_event_loop``, and is ignored if ``loop_factory`` is passed
a value other than ``None``)
**Trio**: options covered in the
`official documentation
<https://trio.readthedocs.io/en/stable/reference-core.html#trio.run>`_
.. versionchanged:: 3.2.0
The default value of ``use_uvloop`` was changed to ``False``.
.. versionchanged:: 4.0.0
The ``policy`` option was replaced with ``loop_factory``.
.. _uvloop: https://pypi.org/project/uvloop/
Using native async libraries
----------------------------
AnyIO lets you mix and match code written for AnyIO and code written for the
asynchronous framework of your choice. There are a few rules to keep in mind however:
* You can only use "native" libraries for the backend you're running, so you cannot, for
example, use a library written for Trio_ together with a library written for asyncio.
* Tasks spawned by these "native" libraries on backends other than Trio_ are not subject
to the cancellation rules enforced by AnyIO
* Threads spawned outside of AnyIO cannot use :func:`.from_thread.run` to call
asynchronous code
.. _virtualenv: https://docs.python-guide.org/dev/virtualenvs/
.. _Trio: https://github.com/python-trio/trio
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