python asyncio: how to best use lock threads?

Question

Let's imagine I have a thread with an asyncio event loop and other threads running.

I may have to deal with synchronisation between threads with the lock mecanism for instance. But the lock may block the coroutine... And no other tasks (in the asyncio thread) will run concurrently.

What is the solution ? My guess is that a kind of lock primitivve which would be asynchronous could do the job but it does not exist as far as I know.

To be precise: I do not refer to the existing asyncio lock primitive.

We surely need an example. Now it is not clear why are you mixing up threads and asyncio; And what are you going to lock — Sergey Belash
– Sergey Belash, Commented Apr 22, 2017 at 23:31
This question is similar to: Asyncio threadsafe primitives. If you believe it’s different, please edit the question, make it clear how it’s different and/or how the answers on that question are not helpful for your problem. — Ilya Egorov
– Ilya Egorov, Commented Nov 21, 2024 at 21:51

Delgan · Accepted Answer · 2023-07-08 08:08:31Z

2

Use loop.run_in_executor to run a synchronous call in a thread:

def synchronous_function():
    with synchronous_lock:
        # Do something

async def asynchronous_function():
    await loop.run_in_executor(None, synchronous_function)

edited Jul 8, 2023 at 8:08

Delgan

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answered Apr 3, 2017 at 23:02

Vincent

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Ilya Egorov · Accepted Answer · 2025-11-06 19:20:12Z

Now an async-aware lock exists. You can use aiologic.BinarySemaphore as the fastest lock implementation provided by the corresponding package (I'm the creator of aiologic). It's similar to threading.Lock, and it never block the event loop:

import asyncio

from threading import Timer

import aiologic

lock = aiologic.BinarySemaphore()


async def a():
    print("before enter")

    async with lock:
        pass

    print("after exit")


async def b():
    print("another task")


async def main():
    async with asyncio.TaskGroup() as tasks:
        lock.green_acquire()

        tasks.create_task(a())
        tasks.create_task(b())

        Timer(1, lock.green_release).start()


asyncio.run(main())  # will take 1 second

But unlike threading.Lock, it omits checks for redundant release() calls. If you need them, you can use aiologic.Semaphore(max_value=1) instead.

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