【六】协程并发
定义tasks时可以设置多个ensure，也可以像多线程那样用append方法实现
tasks = [
asyncio.ensure_future(coroutine1),
asyncio.ensure_future(coroutine2),
asyncio.ensure_future(coroutine3)
]
for i in range(4, 6):
tasks.append(asyncio.ensure_future(do_some_work(i)))
当遇到阻塞时可以使用await让其他协程继续工作
例如：
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(3)
tasks = [
asyncio.ensure_future(coroutine1),
asyncio.ensure_future(coroutine2),
asyncio.ensure_future(coroutine3)
]
for i in range(4, 6):
tasks.append(asyncio.ensure_future(do_some_work(i)))
loop = asyncio.get_event_loop()
start = now()
loop.run_until_complete(asyncio.wait(tasks))
for task in tasks:
print('Task ret: ', task.result())
print('TIME: ', now() - start)
通过运行时间可以看出aysncio实现了并发。asyncio.wait(tasks) 也可以使用 asyncio.gather(*tasks) ,前者接受一个task列表，后者接收一堆task。
【七】协程嵌套
使用async可以定义协程，协程用于耗时的io操作，我们也可以封装更多的io操作过程，这样就实现了嵌套的协程，即一个协程中await了另外一个协程，如此连接起来。
例如：
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)
]
dones, pendings = await asyncio.wait(tasks)
for task in dones:
print('Task ret: ', task.result())
start = now()
loop = asyncio.get_event_loop()
loop.run_until_complete(main())
print('TIME: ', now() - start)
如果使用的是 asyncio.gather创建协程对象，那么await的返回值就是协程运行的结果。
#dones, pendings = await asyncio.wait(tasks)
#for task in dones:
#print('Task ret: ', task.result())
results = await asyncio.gather(*tasks)
for result in results:
print('Task ret: ', result)
不在main协程函数里处理结果，直接返回await的内容，那么最外层的run_until_complete将会返回main协程的结果。
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)
或者返回使用asyncio.wait方式挂起协程。
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)
也可以使用asyncio的as_completed方法
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)
]
for task in asyncio.as_completed(tasks):
result = await task
print('Task ret: {}'.format(result))
start = now()
loop = asyncio.get_event_loop()
done = loop.run_until_complete(main())
print('TIME: ', now() - start)
由此可见，协程的调用和组合十分的灵活，我们可以发挥想象尽情的浪
