Unused Awaitable

What it does

Checks for awaitable objects (such as coroutines) used as expression statements without being awaited.

Why is this bad?

Calling an async def function returns a coroutine object. If the coroutine is never awaited, the body of the async function will never execute, which is almost always a bug. Python emits a RuntimeWarning: coroutine was never awaited at runtime in this case.

Examples

async def fetch_data() -> str:
    return "data"


async def main() -> None:
    # Warning: coroutine is not awaited
    fetch_data()  # error
    await fetch_data()  # OK