10python入门——asynico异步
asynico模块
功能
- 异步网络操作
- 并发
- 协程
关键字解释
- event_loop 事件循环：程序开启一个无限循环，把一些函数注册到事件循环上，当满足事件发生的时候，调用相应的协程函数
- coroutine 协程：协程对象，指一个使用async关键字定义的函数，它的调用不会立即执行函数，而是会返回一个协程对象。协程对象需要注册到事件循环，由事件循环调用。
- task 任务：一个协程对象就是一个原生可以挂起的函数，任务则是对协程进一步封装，其中包含了任务的各种状态
- future: 代表将来执行或没有执行的任务的结果。它和task上没有本质上的区别
- async/await 关键字：python3.5用于定义协程的关键字，async定义一个协程，await用于挂起阻塞的异步调用接口。
第一次尝试
import time
import asyncio
# 这是定义异步函数，先记住写法即可
async def hello():
for i in range(5):
time.sleep(1)
print('Hello World:%s' % time.time())
# 创建一个事件loop
loop = asyncio.get_event_loop()
# 将协程加入到事件循环loop
loop.run_until_complete(hello())
创建一个task
创建task后，在task加入事件循环之前为pending状态，当完成后，状态为finished
# -*- coding:utf-8 -*-
# Author : ZRQ
# Data : 2019/6/22 17:09
import asyncio
import time
now = lambda: time.time()
async def do_some_work(x):
print("waiting:", x)
start = now()
coroutine = do_some_work(2)
# 创建一个事件loop
loop = asyncio.get_event_loop()
# 创建task
task = loop.create_task(coroutine)
# task = asyncio.ensure_future(coroutine)
print(task)
# 将task加入事件循环
loop.run_until_complete(task)
print(task)
print("Time:",now()-start)
为任务绑定回调函数
# -*- coding:utf-8 -*-
# Author : ZRQ
# Data : 2019/6/22 17:09
import time
import asyncio
now = lambda : time.time()
async def do_some_work(x):
print("waiting:",x)
return "Done after {}s".format(x)
def callback(future):
print("callback:",future.result())
start = now()
coroutine = do_some_work(2)
loop = asyncio.get_event_loop()
task = asyncio.ensure_future(coroutine)
print(task)
# 绑定回调函数
task.add_done_callback(callback)
print(task)
loop.run_until_complete(task)
print("Time:", now()-start)
waiting: 2
callback: Done after 2s
Time: 0.006999492645263672
阻塞和异步await
使用async可以定义协程对象，使用await可以针对耗时的操作进行挂起，就像生成器里的yield一样，函数让出控制权。协程遇到await，事件循环将会挂起该协程，执行别的协程，等await后面的操作处理完再回来
# -*- coding:utf-8 -*-
# Author : ZRQ
# Data : 2019/6/22 17:14
import asyncio
import time
now = lambda :time.time()
async def do_some_work(x):
print("waiting:",x)
# await 后面就是调用耗时的操作
await asyncio.sleep(x)
print(x)
return "Done after {}s".format(x)
start = now()
coroutine1 = do_some_work(2)
coroutine2 = do_some_work(0)
loop = asyncio.get_event_loop()
tasks = [
asyncio.ensure_future(coroutine1),
asyncio.ensure_future(coroutine2)
]
loop.run_until_complete(asyncio.wait(tasks))
# 2个协程都执行完，才进行下面语句
for task in tasks:
print("Task ret:",task.result())
print("Time:", now() - start)
从输出0，看出遇到阻塞，就执行下一个协程
waiting: 2
waiting: 0
0
2
Task ret: Done after 2s
Task ret: Done after 0s
Time: 2.009284734725952
并行
2种方式获取函数返回值
# -*- coding:utf-8 -*-
# Author : ZRQ
# Data : 2019/6/22 19:05
import asyncio
import time
now = lambda: time.time()
async def do_some_work(x):
print("waiting:",x)
await asyncio.sleep(x)
return "Done after {}s".format(x)
async def main():
coroutine1 = do_some_work(1)
coroutine2 = do_some_work(2)
coroutine3 = do_some_work(4)
tasks = [
asyncio.ensure_future(coroutine1),
asyncio.ensure_future(coroutine2),
asyncio.ensure_future(coroutine3)
]
return await asyncio.gather(*tasks)
start = now()
loop = asyncio.get_event_loop()
results = loop.run_until_complete(main())
for result in results:
print("Task ret:",result)
print("Time:", now()-start)
waiting: 1
waiting: 2
waiting: 4
Task ret: Done after 1s
Task ret: Done after 2s
Task ret: Done after 4s
Time: 4.009031534194946
# -*- coding:utf-8 -*-
# Author : ZRQ
# Data : 2019/6/22 19:07
import asyncio
import time
now = lambda: time.time()
async def do_some_work(x):
print("waiting:",x)
await asyncio.sleep(x)
return "Done after {}s".format(x)
async def main():
coroutine1 = do_some_work(1)
coroutine2 = do_some_work(2)
coroutine3 = do_some_work(4)
tasks = [
asyncio.ensure_future(coroutine1),
asyncio.ensure_future(coroutine2),
asyncio.ensure_future(coroutine3)
]
return await asyncio.wait(tasks)
start = now()
loop = asyncio.get_event_loop()
done,pending = loop.run_until_complete(main())
for task in done:
print("Task ret:",task.result())
print("Time:", now()-start)
协程停止处理
先遍历取消事件，停止循环，在重启事件循环，最后在close，不然还会抛出异常
# -*- coding:utf-8 -*-
# Author : ZRQ
# Data : 2019/6/22 19:09
import asyncio
import time
now = lambda :time.time()
async def do_some_work(x):
print("Waiting:",x)
await asyncio.sleep(x)
return "Done after {}s".format(x)
coroutine1 =do_some_work(1)
coroutine2 =do_some_work(2)
coroutine3 =do_some_work(2)
tasks = [
asyncio.ensure_future(coroutine1),
asyncio.ensure_future(coroutine2),
asyncio.ensure_future(coroutine3),
]
start = now()
loop = asyncio.get_event_loop()
try:
loop.run_until_complete(asyncio.wait(tasks))
except KeyboardInterrupt as e:
print(asyncio.Task.all_tasks())
for task in asyncio.Task.all_tasks():
print(task.cancel())
loop.stop()
loop.run_forever()
finally:
loop.close()
print("Time:",now()-start)
线程加协程
实现动态添加协程
# -*- coding:utf-8 -*-
# Author : ZRQ
# Data : 2019/6/22 18:35
import asyncio
import time
from threading import Thread
now = lambda :time.time()
def start_loop(loop):
asyncio.set_event_loop(loop)
loop.run_forever()
async def do_some_work(x):
print('Waiting {}'.format(x))
await asyncio.sleep(x)
print('Done after {}s'.format(x))
def more_work(x):
print('More work {}'.format(x))
time.sleep(x)
print('Finished more work {}'.format(x))
start = now()
new_loop = asyncio.new_event_loop()
t = Thread(target=start_loop, args=(new_loop,))
t.start()
print('TIME: {}'.format(time.time() - start))
# 不阻塞
asyncio.run_coroutine_threadsafe(do_some_work(6), new_loop)
asyncio.run_coroutine_threadsafe(do_some_work(4), new_loop)
#阻塞
#new_loop.call_soon_threadsafe(more_work, 6)
#new_loop.call_soon_threadsafe(more_work, 3)
主线程中创建一个new_loop，然后在另外的子线程中开启一个无限事件循环。 主线程通过run_coroutine_threadsafe新注册协程对象。这样就能在子线程中进行事件循环的并发操作