将 asyncio 用于并行任务

Question

我想知道如何使用 asyncio 来处理类似于 nodeJS 所做的任务。我想在不打开线程的情况下同时执行运行个任务。示例：

import asyncio

@asyncio.coroutine
def my_coroutine(task_name, seconds_to_sleep=3):
    print('{0} sleeping for: {1} seconds'.format(task_name, seconds_to_sleep))
    yield from asyncio.sleep(seconds_to_sleep)
    print('{0} is finished'.format(task_name))


loop = asyncio.get_event_loop()
tasks = [
    my_coroutine('task1', 4),
    my_coroutine('task2', 3),
    my_coroutine('task3', 2)]
loop.run_until_complete(asyncio.wait(tasks))
loop.close()

将输出：

task1 sleeping for: 4 seconds
task2 sleeping for: 3 seconds
task3 sleeping for: 2 seconds
task3 is finished
task2 is finished
task1 is finished

但是当我尝试用不同的任务来完成它时，它不会那样工作。

import asyncio
import timeit

@asyncio.coroutine
def my_coroutine(task_name):
    print('order placed for ' + task_name)
    print(timeit.timeit('1 + 3 ', number=50000000))
    print(task_name + ' done')


loop = asyncio.get_event_loop()
tasks = [
    my_coroutine('task1'),
    my_coroutine('task2'),
    my_coroutine('task3')]
loop.run_until_complete(asyncio.wait(tasks))
loop.close()

产出

order placed for task2
0.6677237730912453
task2 done
order placed for task1
0.6627442526498016
task1 done
order placed for task3
0.665618849882418
task3 done

Answer 1

asyncio 不会运行并行处理。它运行是一个任务，直到它等待，然后才转到下一个任务。第一个示例中的 sleep 是使任务相互产生控制的原因。你的第二个例子不等待任何东西，所以每个任务运行s 直到事件循环可以控制另一个任务之前完成。

如果你在你的协程中添加一些可等待的东西（例如，asyncio.sleep），每个人都会放弃控制权，让其他人有机会运行。

@asyncio.coroutine
def my_coroutine(task_name):
    print('order placed for ' + task_name)
    yield from asyncio.sleep(0)  # Another coroutine will resume here.
    print(timeit.timeit('1 + 3 ', number=50000000))
    yield from asyncio.sleep(0)  # Another coroutine will resume here.
    print(task_name + ' done')

将 asyncio 用于并行任务

use asyncio for parallel tasks

python

python-3.x

python-asyncio