python18协程

 

 

 

 

 

 

协程是我们自己调度的
进程是系统调度的
协程切换很少开销

 

 python3.5之前的实现方法

def yield_test():
    """实现协程函数"""
    while True:
        n = (yield)
        print(n)

if __name__ == "__main__":
    rest = yield_test()
    next(rest)
    rest.send("666")
    rest.send("666")

结果：
666
666

 

python3.6之后

 

 

 

 

例如当我们读文件的时候，文件比较大，读的时候可能会有阻塞，这时候我们使用await方法，让loop调用其他的协程，
等到读完之后再回来执行

 

 

import asyncio


async def do_sth(x):
    """定义协程函数"""
    print("等待中{}".format(x))
    await asyncio.sleep(x)

#判断是否为协程函数
print(asyncio.iscoroutinefunction(do_sth))


coroutine = do_sth(5)
#事件循环队列
loop = asyncio.get_event_loop()
#注册任务
task = loop.create_task(coroutine)
print(task)
#等待协程任务执行结束
loop.run_until_complete(task)
print(task)


结果；
True
<Task pending coro=<do_sth() running at D:/PycharmProjects/untitled0406/test.py:4>>
等待中5
<Task finished coro=<do_sth() done, defined at D:/PycharmProjects/untitled0406/test.py:4> result=None>

 

执行过程

创建协程函数
获取事件循环队列
将协程函数加入到事件队列形成任务
等待协程任务执行结束

　　

 

 

import asyncio

async def compute(x,y):
    print("计算x + y => {0}+{1}".format(x,y))
    await asyncio.sleep(3)
    return x + y


async def get_sum(x,y):
    rest = await compute(x,y)
    print("{0} + {1} = {2}".format(x,y,rest))


#拿到事件循环
loop = asyncio.get_event_loop()
loop.run_until_complete(get_sum(1,2))
loop.close()


结果：
计算x + y => 1+2
1 + 2 = 3

 

 

#定义一个队列
#让两个协程来进行通信
#让其中一个协程往队列中写数据
#让另一个协程从队列中删除数据
import asyncio
import random


async def add(store,name):
    """
    写入数据到队列
    :param store: 队列的对象
    :return:
    """
    for i in range(5):
        #往队列添加数字
        num = "{0} - {1}".format(name,i)
        await asyncio.sleep(random.randint(1, 5))
        await store.put(i)
        print("{2}add one ... {0},size:{1}".format(num,store.qsize(),name))


async def reduce(store):
    """
    从队列中删除数据
    :param store:
    :return:
    """
    for i in range(10):
        rest = await store.get()
        print("reduce one ....{0},size{1}".format(rest,store.qsize()))


if __name__ == "__main__":
    #准备队列
    store = asyncio.Queue(maxsize=5)
    a1 = add(store,"a1111")
    a2 = add(store,"a2222")
    r1 = reduce(store)
    #添加事件队列
    loop = asyncio.get_event_loop()
    loop.run_until_complete(asyncio.gather(a1,a2,r1))
    loop.close()

结果；

a2222add one ... a2222 - 0,size:1
reduce one ....0,size0
a1111add one ... a1111 - 0,size:1
reduce one ....0,size0
a2222add one ... a2222 - 1,size:1
reduce one ....1,size0
a1111add one ... a1111 - 1,size:1
reduce one ....1,size0
a1111add one ... a1111 - 2,size:1
reduce one ....2,size0
a2222add one ... a2222 - 2,size:1
a1111add one ... a1111 - 3,size:2
reduce one ....2,size1
reduce one ....3,size0
a1111add one ... a1111 - 4,size:1
reduce one ....4,size0
a2222add one ... a2222 - 3,size:1
reduce one ....3,size0
a2222add one ... a2222 - 4,size:1
reduce one ....4,size0