blocking-open-call-in-async-function (ASYNC230)

Derived from the flake8-async linter.

What it does

Checks that async functions do not open files with blocking methods like open.

Why is this bad?

Blocking an async function via a blocking call will block the entire event loop, preventing it from executing other tasks while waiting for the call to complete, negating the benefits of asynchronous programming.

Instead of making a blocking call, use an equivalent asynchronous library or function.

Example

async def foo():
    with open("bar.txt") as f:
        contents = f.read()

Use instead:

import anyio


async def foo():
    async with await anyio.open_file("bar.txt") as f:
        contents = await f.read()