yield 异步 并行 Promise await async

时间：2023-03-09 22:55:45
yield 异步 并行 Promise await async

yield方式转移执行权的协程之间不是调用者与被调用者的关系，而是彼此对称、平等的

http://www.geeksforgeeks.org/use-yield-keyword-instead-return-keyword-python/

def simpleGeneratorFun():
    yield 1
    yield 2
    yield 3

for value in simpleGeneratorFun():
    print(value)

print('-----')

def nextSquare():
    i = 1
    while True:
        yield i * i
        i += 1

for num in nextSquare():
    if num > 100:
        break
    print(num)

Python yield 使用浅析 https://www.ibm.com/developerworks/cn/opensource/os-cn-python-yield/

GitHub - gevent/gevent: Coroutine-based concurrency library for Python https://github.com/gevent/gevent

gevent - 廖雪峰的官方网站 https://www.liaoxuefeng.com/wiki/001374738125095c955c1e6d8bb493182103fac9270762a000/001407503089986d175822da68d4d6685fbe849a0e0ca35000

Python通过yield提供了对协程的基本支持，但是不完全。而第三方的gevent为Python提供了比较完善的协程支持。

gevent是第三方库，通过greenlet实现协程，其基本思想是：

当一个greenlet遇到IO操作时，比如访问网络，就自动切换到其他的greenlet，等到IO操作完成，再在适当的时候切换回来继续执行。由于IO操作非常耗时，经常使程序处于等待状态，有了gevent为我们自动切换协程，就保证总有greenlet在运行，而不是等待IO。

version = 3.7.4

协程创建 任务执行
Coroutines and Tasks — Python 3.7.4 documentation https://docs.python.org/3/library/asyncio-task.html#creating-tasks
# 协程通过 async/await 语法进行声明，是编写异步应用的推荐方式。
# Coroutines declared with async/await syntax is the preferred way of writing asyncio applications.
import asyncio

import time, random

def taskPool():

    '''

    任务池

    一个任务一个协程

    :return:

    '''

    return [i for i in range(random.randint(0, 32))]

# 协程通过 async/await 语法进行声明，是编写异步应用的推荐方式。

# Coroutines declared with async/await syntax is the preferred way of writing asyncio applications.

async def executeSingleTask(taskId, delay=10):

    print(f'taskId {taskId} started at {time.strftime("%X")}')

    await asyncio.sleep(delay)

    print(f'taskId {taskId} finished at {time.strftime("%X")}')

async def executeAllTask():

    # 获取任务

    taskList, awaitList = taskPool(), []

    # 异步任务创建

    for taskId in taskList:

        task = asyncio.create_task(executeSingleTask(taskId))

        awaitList.append(task)

    # 异步任务执行

    for a in awaitList:

        await a

asyncio.run(executeAllTask())

　　






D:\pyCGlang\venv\异步\Scripts\python.exe D:/pyCGlang/异步/a.py

taskId 0 started at 00:11:36

taskId 1 started at 00:11:36

taskId 2 started at 00:11:36

taskId 3 started at 00:11:36

taskId 4 started at 00:11:36

taskId 5 started at 00:11:36

taskId 6 started at 00:11:36

taskId 7 started at 00:11:36

taskId 8 started at 00:11:36

taskId 9 started at 00:11:36

taskId 10 started at 00:11:36

taskId 11 started at 00:11:36

taskId 12 started at 00:11:36

taskId 13 started at 00:11:36

taskId 14 started at 00:11:36

taskId 15 started at 00:11:36

taskId 16 started at 00:11:36

taskId 17 started at 00:11:36

taskId 18 started at 00:11:36

taskId 19 started at 00:11:36

taskId 20 started at 00:11:36

taskId 21 started at 00:11:36

taskId 22 started at 00:11:36

taskId 0 finished at 00:11:46

taskId 2 finished at 00:11:46

taskId 6 finished at 00:11:46

taskId 14 finished at 00:11:46

taskId 22 finished at 00:11:46

taskId 21 finished at 00:11:46

taskId 20 finished at 00:11:46

taskId 19 finished at 00:11:46

taskId 18 finished at 00:11:46

taskId 17 finished at 00:11:46

taskId 16 finished at 00:11:46

taskId 13 finished at 00:11:46

taskId 15 finished at 00:11:46

taskId 12 finished at 00:11:46

taskId 11 finished at 00:11:46

taskId 10 finished at 00:11:46

taskId 9 finished at 00:11:46

taskId 8 finished at 00:11:46

taskId 5 finished at 00:11:46

taskId 7 finished at 00:11:46

taskId 4 finished at 00:11:46

taskId 1 finished at 00:11:46

taskId 3 finished at 00:11:46

Process finished with exit code 0





　　


效果上实现了10个任务的并行执行




import asyncio

import time, random

def taskPool():

    '''

    任务池

    一个任务一个协程

    :return:

    '''

    return [i for i in range(random.randint(0, 32))]

# 协程通过 async/await 语法进行声明，是编写异步应用的推荐方式。

# Coroutines declared with async/await syntax is the preferred way of writing asyncio applications.

async def executeSingleTask(taskId, delay=10):

    print(f'taskId {taskId} started at {time.strftime("%X")}---{time.time()}')

    await asyncio.sleep(delay)

    print(f'taskId {taskId} finished at {time.strftime("%X")}---{time.time()}')

async def executeAllTask():

    # 获取任务

    taskList, awaitList = taskPool(), []

    # 异步任务创建

    for taskId in taskList:

        task = asyncio.create_task(executeSingleTask(taskId))

        awaitList.append(task)

    # 异步任务执行

    for a in awaitList:

        await a

asyncio.run(executeAllTask())





　　




D:\pyCGlang\venv\异步\Scripts\python.exe D:/pyCGlang/异步/a.py

taskId 0 started at 00:28:34---1567528114.565263

taskId 1 started at 00:28:34---1567528114.565263

taskId 2 started at 00:28:34---1567528114.565263

taskId 3 started at 00:28:34---1567528114.565263

taskId 4 started at 00:28:34---1567528114.565263

taskId 5 started at 00:28:34---1567528114.565263

taskId 6 started at 00:28:34---1567528114.565263

taskId 7 started at 00:28:34---1567528114.566263

taskId 8 started at 00:28:34---1567528114.566263

taskId 9 started at 00:28:34---1567528114.566263

taskId 10 started at 00:28:34---1567528114.566263

taskId 11 started at 00:28:34---1567528114.566263

taskId 12 started at 00:28:34---1567528114.566263

taskId 0 finished at 00:28:44---1567528124.5508342

taskId 2 finished at 00:28:44---1567528124.5508342

taskId 5 finished at 00:28:44---1567528124.5508342

taskId 1 finished at 00:28:44---1567528124.5508342

taskId 4 finished at 00:28:44---1567528124.5508342

taskId 3 finished at 00:28:44---1567528124.5508342

taskId 6 finished at 00:28:44---1567528124.566835

taskId 12 finished at 00:28:44---1567528124.566835

taskId 11 finished at 00:28:44---1567528124.566835

taskId 7 finished at 00:28:44---1567528124.566835

taskId 10 finished at 00:28:44---1567528124.566835

taskId 9 finished at 00:28:44---1567528124.566835

taskId 8 finished at 00:28:44---1567528124.566835

Process finished with exit code 0





　　


https://developers.google.com/web/fundamentals/primers/async-functions




function now(){

  const c=(new Date()) +(new Date().getMilliseconds());

  console.log(c);

}

function wait(ms) {

  now();

  return new Promise(r => setTimeout(r, ms));

}

async function parallel() {

  console.log("start!--->");

  now();

  const wait1 = wait(6000); // Start a 6000ms timer asynchronously…

  const wait2 = wait(6000); // …meaning this timer happens in parallel.

  await wait1; // Wait 6000ms for the first timer…

  await wait2; // …by which time this timer has already finished.

  console.log("<---done!");

  now();

  return "done!";

}

parallel();





　　




start!--->

VM125:4 Thu Sep 05 2019 20:19:24 GMT+0800 (新加坡标准时间)110

VM125:4 Thu Sep 05 2019 20:19:24 GMT+0800 (新加坡标准时间)110

VM125:4 Thu Sep 05 2019 20:19:24 GMT+0800 (新加坡标准时间)110

Promise {<pending>}__proto__: Promise[[PromiseStatus]]: "resolved"[[PromiseValue]]: "done!"

VM125:17 <---done!

VM125:4 Thu Sep 05 2019 20:19:30 GMT+0800 (新加坡标准时间)112





　　


https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Guide/Using_promises


在 ECMAScript 2017 标准的 async/await 语法糖中，这种同步形式代码的对称性得到了极致的体现：




async function foo() {

  try {

    let result = await doSomething();

    let newResult = await doSomethingElse(result);

    let finalResult = await doThirdThing(newResult);

    console.log(`Got the final result: ${finalResult}`);

  } catch(error) {

    failureCallback(error);

  }

}





　　


　　




相关文章