First Steps with AnyIO¶

Asyncer is based on AnyIO, so let's start with a simple example just using AnyIO to write async code.

A Main Function¶

Let's start with a simple main async function.

# Code above omitted 👆

async def main():
    message = await do_work(name="World")
    return message

# Code below omitted 👇

👀 Full file preview

import anyio


async def do_work(name: str):
    await anyio.sleep(1)
    return f"Hello, {name}"


async def main():
    message = await do_work(name="World")
    return message


result = anyio.run(main)
print(result)

When working with async code you normally use async and await.

The main rules are that:

You can only use await inside async functions.
To call an async function, you need to use await in front of it.

In this case, we can use await inside of main() because it is an async function.

Call Async Functions¶

The function do_work() also needs to be declared with async def for us to be able to await for its result when calling it.

do_work() could be talking to a database, calling an API, or something else that needs to wait for something.

For this example, let's simulate that by making do_work() wait there for 1 second:

# Code above omitted 👆

async def do_work(name: str):
    await anyio.sleep(1)
    return f"Hello, {name}"


async def main():
    message = await do_work(name="World")
    return message

# Code below omitted 👇

👀 Full file preview

import anyio


async def do_work(name: str):
    await anyio.sleep(1)
    return f"Hello, {name}"


async def main():
    message = await do_work(name="World")
    return message


result = anyio.run(main)
print(result)

Run the Main Function¶

As main() is an async function, we can't call it directly because we can't await it. Instead, we call it with anyio.run():

import anyio


async def do_work(name: str):
    await anyio.sleep(1)
    return f"Hello, {name}"


async def main():
    message = await do_work(name="World")
    return message


result = anyio.run(main)
print(result)

anyio.run() will do everything necessary to call main(), handling all the await parts, and waiting there until it finishes.

Run the Program in the Command Line¶

If you run that, you will see the expected result, it will wait for 1 second and then print Hello, World:

$ python main.py

// Wait for it...

// After around one second
Hello, World

Next Steps¶

Great! That's already a first async program. 🚀

Now let's start updating the example and see in which cases Asyncer could be useful.