Python中的asyncio代码详解

zuanfengxiao

2019-09-07

asyncioä»ç»

asyncioä¸çåºæ¬æ¦å¿µ

Eventloop

Coroutine

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import asyncio
import time
async def a():
 print('Suspending a')
 await asyncio.sleep(3)
 print('Resuming a')
async def b():
 print('Suspending b')
 await asyncio.sleep(1)
 print('Resuming b')
async def main():
 start = time.perf_counter()
 await asyncio.gather(a(), b())
 print(f'{main.__name__} Cost: {time.perf_counter() - start}')
if __name__ == '__main__':
 asyncio.run(main())

æ§è¡ä¸è¿°ä»£ç ï¼å¯ä»¥çå°ç±»ä¼¼è¿æ ·çè¾åº:

Suspending a
Suspending b
Resuming b
Resuming a
main Cost: 3.0023356619999997

Future

>>> import asyncio
>>> def fun():
...  print("inner fun")
...  return 111
... 
>>> loop = asyncio.get_event_loop()
>>> future = loop.run_in_executor(None, fun) #è¿éæ²¡æä½¿ç¨await
inner fun
>>> future #å¯ä»¥çå°ï¼funæ¹æ³ç¶ææ¯pending
<Future pending cb=[_chain_future.<locals>._call_check_cancel() at /usr/local/Cellar/python/3.7.3/Frameworks/Python.framework/Versions/3.7/lib/python3.7/asyncio/futures.py:348]>
>>> future.done() # è¿æ²¡æå®æ
False
>>> [m for m in dir(future) if not m.startswith('_')]
['add_done_callback', 'cancel', 'cancelled', 'done', 'exception', 'get_loop', 'remove_done_callback', 'result', 'set_exception', 'set_result']
>>> future.result() #è¿ä¸ªæ¶åå¦æç´æ¥è°ç¨result()æ¹æ³ä¼æ¥é
Traceback (most recent call last):
 File "<input>", line 1, in <module>
asyncio.base_futures.InvalidStateError: Result is not set.
>>> async def runfun():
...  result=await future
...  print(result)
...  
>>>loop.run_until_complete(runfun()) #ä¹å¯ä»¥éè¿ loop.run_until_complete(future) æ¥æ§è¡ï¼è¿éåªæ¯ä¸ºäºæ¼ç¤ºawait
111
>>> future
<Future finished result=111>
>>> future.done()
True
>>> future.result()
111
Task

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>>> async def a():
...  print('Suspending a')
...  await asyncio.sleep(3)
...  print('Resuming a')
...  
>>> task = asyncio.ensure_future(a())
>>> loop.run_until_complete(task)
Suspending a
Resuming a

asyncioä¸ä¸äºå¸¸è§ç¨æ³çåºå«

Asyncio.gatheråasyncio.wait

>>> import asyncio
>>> async def a():
...  print('Suspending a')
...  await asyncio.sleep(3)
...  print('Resuming a')
...  return 'A'
... 
... 
... async def b():
...  print('Suspending b')
...  await asyncio.sleep(1)
...  print('Resuming b')
...  return 'B'
... 
>>> async def fun1():
...  return_value_a, return_value_b = await asyncio.gather(a(), b())
...  print(return_value_a,return_value_b)
...  
>>> asyncio.run(fun1())
Suspending a
Suspending b
Resuming b
Resuming a
A B
>>> async def fun2():
...  done,pending=await asyncio.wait([a(),b()])
...  print(done)
...  print(pending)
...  task=list(done)[0]
...  print(task)
...  print(task.result())
...  
>>> asyncio.run(fun2())
Suspending b
Suspending a
Resuming b
Resuming a
{<Task finished coro=<a() done, defined at <input>:1> result='A'>, <Task finished coro=<b() done, defined at <input>:8> result='B'>}
set()
<Task finished coro=<a() done, defined at <input>:1> result='A'>
A

æ ¹æ®ä¸è¿°ä»£ç ï¼æä»¬å¯ä»¥çåºä¸¤èçåºå«ï¼

asyncio.wait æ¯ææ¥åä¸ä¸ªåæ° return_when ï¼å¨é»è®¤æåµä¸ï¼ asyncio.wait ä¼çå¾å¨é¨ä»»å¡å®æ (return_when='ALL_COMPLETED') ï¼å®è¿æ¯æ FIRST_COMPLETED ï¼ç¬¬ä¸ä¸ªåç¨å®æå°±è¿åï¼å FIRST_EXCEPTION ï¼åºç°ç¬¬ä¸ä¸ªå¼å¸¸å°±è¿åï¼ï¼

>>> async def fun2():
...  done,pending=await asyncio.wait([a(),b()],return_when=asyncio.tasks.FIRST_COMPLETED)
...  print(done)
...  print(pending)
...  task=list(done)[0]
...  print(task)
...  print(task.result())
...  
>>> asyncio.run(fun2())
Suspending a
Suspending b
Resuming b
{<Task finished coro=<b() done, defined at <input>:8> result='B'>}
{<Task pending coro=<a() running at <input>:3> wait_for=<Future pending cb=[<TaskWakeupMethWrapper object at 0x10757bf18>()]>>}
<Task finished coro=<b() done, defined at <input>:8> result='B'>
B

ä¸è¬æåµä¸ï¼ç¨ asyncio.gather å°±è¶³å¤äºã

asyncio.create_taskåloop.create_taskä»¥åasyncio.ensure_future

è¿ä¸ç§æ¹æ³é½å¯ä»¥åå»º Task ,ä»Python3.7å¼å§å¯ä»¥ç»ä¸çä½¿ç¨æ´é«é¶ç asyncio.create_task .å¶å® asyncio.create_task å°±æ¯ç¨ç loop.create_task . loop.create_task æ¥åçåæ°éè¦æ¯ä¸ä¸ªåç¨ï¼ä½æ¯ asyncio.ensure_future é¤äºæ¥ååç¨ï¼è¿å¯ä»¥æ¯ Future å¯¹è±¡æè awaitable å¯¹è±¡ï¼

å¦æåæ°æ¯åç¨ï¼å¶åºå±ä½¿ç¨ loop.create_task ï¼è¿å Task å¯¹è±¡
å¦ææ¯ Future å¯¹è±¡ä¼ç´æ¥è¿å
å¦ææ¯ä¸ä¸ª awaitable å¯¹è±¡ï¼ä¼ await è¿ä¸ªå¯¹è±¡ç __await__ æ¹æ³ï¼åæ§è¡ä¸æ¬¡ ensure_future ï¼æåè¿å Task æè Future ã

æä»¥ ensure_future æ¹æ³ä¸»è¦å°±æ¯ç¡®ä¿è¿æ¯ä¸ä¸ª Future å¯¹è±¡ï¼ä¸è¬æåµä¸ç´æ¥ç¨ asyncio.create_task å°±å¯ä»¥äºã

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å¯ä»¥ä½¿ç¨ add_done_callback æ¥æ·»å æååè°ï¼

def callback(future):
 print(f'Result: {future.result()}')
def callback2(future, n):
 print(f'Result: {future.result()}, N: {n}')
async def funa():
 await asyncio.sleep(1)
 return "funa"
async def main():
 task = asyncio.create_task(funa())
 task.add_done_callback(callback)
 await task
 #è¿æ ·å¯ä»¥ä¸ºcallbackä¼ éåæ°
 task = asyncio.create_task(funa())
 task.add_done_callback(functools.partial(callback2, n=1))
 await task
if __name__ == '__main__':
 asyncio.run(main())

æ§è¡åæ¥ä»£ç

def a1():
 time.sleep(1)
 return "A"
async def b1():
 await asyncio.sleep(1)
 return "B"
async def main():
 loop = asyncio.get_running_loop()
 await asyncio.gather(loop.run_in_executor(None, a1), b1())
if __name__ == '__main__':
 start = time.perf_counter()
 asyncio.run(main())
 print(f'main method Cost: {time.perf_counter() - start}')
# è¾åºï¼ main method Cost: 1.0050589740000002

å¯ä»¥ä½¿ç¨ run_into_executor æ¥å°åæ¥å½æ°é»è¾è½¬åæä¸ä¸ªåç¨ï¼ç¬¬ä¸ä¸ªåæ°æ¯è¦ä¼ é concurrent.futures.Executor å®ä¾çï¼ä¼ é None ä¼éæ©é»è®¤ç executor ã

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async python

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Python中的asyncio代码详解

zuanfengxiao

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