The basics¶
AnyIO requires Python 3.6.2 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:
pip install anyio
To install a supported version of trio or curio, you can use install them as extras like this:
pip install anyio[curio]
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 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)
Backend specific options¶
Asyncio:
debug
(bool
, default=False): Enables debug mode in the event loopuse_uvloop
(bool
, default=True): Use the faster uvloop event loop implementation, if availablepolicy
(AbstractEventLoopPolicy
, default=None): the event loop policy instance to use for creating a new event loop (overridesuse_uvloop
)
Curio: options covered in the official documentation
Trio: options covered in the official documentation
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
run_async_from_thread()
to call asynchronous code