[英]How to use asyncio for parallel tasks
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运行任务。 例子:
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 output:
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
asyncio不会并行运行。 它运行一个任务,直到等待,然后继续下一个任务。 第一个例子中的sleep
是使任务相互控制的原因。 您的第二个示例没有等待任何内容,因此每个任务都会运行直到完成,然后事件循环才能控制另一个任务。
如果你将一些等待的东西(例如, asyncio.sleep
)添加到你的协程中,每一个都会产生控制并让其他人有机会跑。
@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')
asyncio 文档如下所述,因此asyncio 任务同时运行但不是并行运行。
asyncio 是一个使用 async/await 语法编写并发代码的库。
并且, @asyncio.coroutine自Python 3.7.14起被弃用,自Python 3.11.0起被删除,因此您应该使用async
,如下所示:
# @asyncio.coroutine
async def test():
print("Test")
例如,使用以下代码:
import asyncio
async def test1():
for _ in range(0, 3):
print("Test1")
async def test2():
for _ in range(0, 3):
print("Test2")
async def test3():
for _ in range(0, 3):
print("Test3")
async def call_tests():
await asyncio.gather(test1(), test2(), test3())
asyncio.run(call_tests())
test1()
、 test2()
和test3()
运行,如下所示:
Test1 # 0 second
Test1 # 0 second
Test1 # 0 second
Test2 # 0 second
Test2 # 0 second
Test2 # 0 second
Test3 # 0 second
Test3 # 0 second
Test3 # 0 second
并且,如果在其中使用await asyncio.sleep(1)
,如下所示:
import asyncio
async def test1():
for _ in range(0, 3):
print("Test1")
await asyncio.sleep(1) # Here
async def test2():
for _ in range(0, 3):
print("Test2")
await asyncio.sleep(1) # Here
async def test3():
for _ in range(0, 3):
print("Test3")
await asyncio.sleep(1) # Here
async def call_tests():
await asyncio.gather(test1(), test2(), test3())
asyncio.run(call_tests())
它们交替运行,每次休眠 1 秒,如下所示:
Test1 # 1 second
Test2 # 1 second
Test3 # 1 second
Test1 # 2 seconds
Test2 # 2 seconds
Test3 # 2 seconds
Test1 # 3 seconds
Test2 # 3 seconds
Test3 # 3 seconds
并且,如果在其中使用await asyncio.sleep(0)
,如下所示:
import asyncio
async def test1():
for _ in range(0, 3):
print("Test1")
await asyncio.sleep(0) # Here
async def test2():
for _ in range(0, 3):
print("Test2")
await asyncio.sleep(0) # Here
async def test3():
for _ in range(0, 3):
print("Test3")
await asyncio.sleep(0) # Here
async def call_tests():
await asyncio.gather(test1(), test2(), test3())
asyncio.run(call_tests())
它们在不休眠的情况下交替运行,如下所示:
Test1 # 0 second
Test2 # 0 second
Test3 # 0 second
Test1 # 0 second
Test2 # 0 second
Test3 # 0 second
Test1 # 0 second
Test2 # 0 second
Test3 # 0 second
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