如何使用滚动协程永远在其上运行来创建事件循环? [英] How to create an event loop with rolling coroutines running on it forever?

问题描述

为了防止上下文切换，我想创建一个大循环以同时服务于网络连接和某些例程.

In order to prevent from context switching, I want to create a big loop to serve both the network connections and some routines.

这是正常功能的实现:

import asyncio
import time


def hello_world(loop):
    print('Hello World')
    loop.call_later(1, hello_world, loop)

def good_evening(loop):
    print('Good Evening')
    loop.call_later(1, good_evening, loop)

print('step: asyncio.get_event_loop()')
loop = asyncio.get_event_loop()

print('step: loop.call_soon(hello_world, loop)')
loop.call_soon(hello_world, loop)
print('step: loop.call_soon(good_evening, loop)')
loop.call_soon(good_evening, loop)

try:
    # Blocking call interrupted by loop.stop()
    print('step: loop.run_forever()')
    loop.run_forever()
except KeyboardInterrupt:
    pass
finally:
    print('step: loop.close()')
    loop.close()

这是协程的实现:

import asyncio


@asyncio.coroutine
def hello_world():
    while True:
        yield from asyncio.sleep(1)
        print('Hello World')

@asyncio.coroutine
def good_evening():
    while True:
        yield from asyncio.sleep(1)
        print('Good Evening')

print('step: asyncio.get_event_loop()')
loop = asyncio.get_event_loop()
try:
    print('step: loop.run_until_complete()')
    loop.run_until_complete(asyncio.wait([
        hello_world(),
        good_evening()
    ]))
except KeyboardInterrupt:
    pass
finally:
    print('step: loop.close()')
    loop.close()

和混合的:

import asyncio
import time


def hello_world(loop):
    print('Hello World')
    loop.call_later(1, hello_world, loop)

def good_evening(loop):
    print('Good Evening')
    loop.call_later(1, good_evening, loop)

@asyncio.coroutine
def hello_world_coroutine():
    while True:
        yield from asyncio.sleep(1)
        print('Hello World Coroutine')

@asyncio.coroutine
def good_evening_coroutine():
    while True:
        yield from asyncio.sleep(1)
        print('Good Evening Coroutine')

print('step: asyncio.get_event_loop()')
loop = asyncio.get_event_loop()

print('step: loop.call_soon(hello_world, loop)')
loop.call_soon(hello_world, loop)
print('step: loop.call_soon(good_evening, loop)')
loop.call_soon(good_evening, loop)
print('step: asyncio.async(hello_world_coroutine)')
asyncio.async(hello_world_coroutine())
print('step: asyncio.async(good_evening_coroutine)')
asyncio.async(good_evening_coroutine())

try:
    loop.run_forever()
except KeyboardInterrupt:
    pass
finally:
    print('step: loop.close()')
    loop.close()

如您所见，每个协程函数都有一个while循环.如何使它像普通的一样? IE.完成后，请在给定的延迟时间后调用自身，而不仅仅是在此处放置循环.

As you see, each coroutine function has a while loop surrounded. How can I make it like the normal one? I.e. when it is done, call itself after the given delay time, but not just put a loop there.

推荐答案

如果您真的想从协程中消除while循环(我不确定您为什么会认为这是必要的；这是最自然的方法您正在尝试执行的操作)，则可以使用 asyncio.async (或者在Python 3.4.4+上为asyncio.ensure_future)以安排协程在下一次事件循环迭代时再次运行:

If you really want to eliminate the while-loop from the coroutines (I'm not sure why you feel that's necessary; it's the most natural way to do what you're trying to do), you can use asyncio.async (or asyncio.ensure_future on Python 3.4.4+) to schedule the coroutine to run again on the next event loop iteration:

import asyncio

@asyncio.coroutine
def hello_world():
    yield from asyncio.sleep(1)
    print('Hello World')
    asyncio.async(hello_world())

@asyncio.coroutine
def good_evening():
    yield from asyncio.sleep(1)
    print('Good Evening')
    asyncio.async(good_evening())

print('step: asyncio.get_event_loop()')
loop = asyncio.get_event_loop()
try:
    print('step: loop.run_until_complete()')
    asyncio.async(hello_world())
    asyncio.async(good_evening())
    loop.run_forever()
except KeyboardInterrupt:
    pass
finally:
    print('step: loop.close()')
    loop.close()

请注意，如果要执行此操作，则必须切换回使用loop.run_forever()，因为hello_world/good_evening将在立即打印后退出.

Note that you have to switch back to using loop.run_forever() if you do this, since hello_world/good_evening will exit immediately after printing now.

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