【asyncio】run_coroutine_threadsafe与run_in_executor多线程操作

run_coroutine_threadsafe

用于在另一个线程中的执行异步方法，需要事先构建一个事件循环 loop ，将 loop 放入线程中 run_forever() ，外部通过方法asyncio.run_coroutine_threadsafe(coro, loop) 让 loop 执行异步方法
coro: 异步方法
loop: 事件循环

import asyncio
import threading
import time


async def function():
    print("function里面")
    return "返回"


def start_loop(loop):
    asyncio.set_event_loop(loop)
    loop.run_forever()


if __name__ == '__main__':
    loop = asyncio.get_event_loop()
    threading.Thread(target=start_loop, args=(loop,), daemon=True).start()

    res = asyncio.run_coroutine_threadsafe(function(), loop)
    print("开始休眠")
    time.sleep(3)
    print(res.result()) # 可以通过result()获取异步函数的返回值，会阻塞，直到异步函数运行结束

运行结果：

开始休眠
function里面
返回

run_in_executor

用于创建一个线程或进程执行同步函数，下列为三种使用情况

---

创建线程池执行函数，无法获取返回值，属性executor传None，默认创建线程执行

import asyncio
import time


def function():
    print("function里面")
    return "返回"


if __name__ == '__main__':
    loop = asyncio.get_event_loop()

	thread_pool_executor = ThreadPoolExecutor()
    res = loop.run_in_executor(thread_pool_executor, function)
    # res = loop.run_in_executor(None, function)  #传None，默认线程，同上
    print("开始休眠")
    time.sleep(3)
    print(res.result())

运行结果：

function里面开始休眠

Traceback (most recent call last):
  File "...test2.py", line 18, in 
    print(res.result())
asyncio.base_futures.InvalidStateError: Result is not set.

---

创建进程池执行函数，无法获取返回值

import asyncio
import time
from concurrent.futures import ProcessPoolExecutor


def function():
    print("function里面")
    time.sleep(10)
    return "返回"


if __name__ == '__main__':
    loop = asyncio.get_event_loop()

    process_pool_executor = ProcessPoolExecutor()
    res = loop.run_in_executor(process_pool_executor, function)
    print("开始休眠")
    time.sleep(3)
    print(res.result())

运行结果：

开始休眠
function里面
Traceback (most recent call last):
  File "...test2.py", line 18, in 
    print(res.result())
asyncio.base_futures.InvalidStateError: Result is not set.

---

在异步函数中用await执行，可以获取返回值，但是会变成同步

import asyncio
import time
from concurrent.futures import ThreadPoolExecutor


def function():
    print("function里面")
    time.sleep(3)
    return "返回"


async def main():
    loop = asyncio.get_event_loop()

    thread_pool_executor = ThreadPoolExecutor()
    res = await loop.run_in_executor(thread_pool_executor, function)
    return res


if __name__ == '__main__':
    res = asyncio.run(main())
    print(res)

运行结果：

function里面
返回