自己在学习协程的时候，对一些东西拿捏的不准，甚至是不解，搞出这样的两个脚本来，让自己更糊涂了，请教了很多人，估计是因为这个问题很愚蠢，所以也没人搭理，后来自己想了想，发现结果很明了，结合之前学习到的理论，有了一些认识
image.png
1.同步脚本在执行的时候，print_time函数总共耗时是3s，因为该函数总共调用3次，每次sleep1s,该sleep操作是阻塞的。
2.协程方式的print_time耗时很少，函数中的sleep操作是非阻塞的。这里结果显示的调用6次，可以以上图那么解释，其实是上下文切换了6次。
# 脚本demo2_1.py
import asyncio
import datetime
import time
@asyncio.coroutine
def print_time():
print(datetime.datetime.now())
yield from asyncio.sleep(1)
@asyncio.coroutine
def display_date(loop):
end_time = loop.time() + 5.0
while True:
yield from print_time()
if (loop.time() + 1.0) >= end_time:
break
yield from asyncio.sleep(1)
return "Coroutine is finished..."
if __name__ =='__main__':
import cProfile
start_time = time.time()
if sys.platform == "win32":
loops = asyncio.ProactorEventLoop()
asyncio.set_event_loop(loops)
else:
loops = asyncio.get_event_loop()
# Blocking call which returns when the hello_world() coroutine is done
try:
cProfile.run("loops.run_until_complete(display_date(loops))")
# print(loops.run_until_complete(display_date(loops)))
# print('Used: ', time.time()-start_time)
except KeyboardInterrupt as e:
for task in asyncio.Task.all_tasks():
print(task.cancel())
loops.stop()
try:
loops.run_forever()
finally:
loops.close()
# 脚本demo2_2.py
import datetime
import time
def print_time():
print(datetime.datetime.now())
time.sleep(1)
def display_date():
end_time = time.time() + 5.0
while True:
print_time()
if (time.time() + 1.0) >= end_time:
break
time.sleep(1)
if __name__ == '__main__':
import cProfile
start_time = time.time()
cProfile.run("display_date()")
print('Used: ', time.time() - start_time)
脚本demo2_1.py的运行结果如下：
2017-08-09 12:14:51.292522
2017-08-09 12:14:53.293397
2017-08-09 12:14:55.293789
421 function calls in 5.002 seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.000 0.000 5.002 5.002 <string>:1(<module>)
1 0.000 0.000 0.000 0.000 _weakrefset.py:38(_remove)
1 0.000 0.000 0.000 0.000 _weakrefset.py:70(__contains__)
2 0.000 0.000 0.000 0.000 _weakrefset.py:81(add)
5 0.000 0.000 0.000 0.000 base_events.py:1325(_timer_handle_cancelled)
12 0.000 0.000 5.002 0.417 base_events.py:1330(_run_once)
2 0.000 0.000 0.000 0.000 base_events.py:1429(_set_coroutine_wrapper)
24 0.000 0.000 0.000 0.000 base_events.py:1462(get_debug)
1 0.000 0.000 0.000 0.000 base_events.py:176(_run_until_complete_cb)
5 0.000 0.000 0.000 0.000 base_events.py:273(create_future)
1 0.000 0.000 0.000 0.000 base_events.py:277(create_task)
15 0.000 0.000 0.000 0.000 base_events.py:355(_check_closed)
1 0.000 0.000 5.002 5.002 base_events.py:404(run_forever)
1 0.000 0.000 5.002 5.002 base_events.py:432(run_until_complete)
1 0.000 0.000 0.000 0.000 base_events.py:469(stop)
1 0.000 0.000 0.000 0.000 base_events.py:514(is_running)
26 0.000 0.000 0.000 0.000 base_events.py:518(time)
5 0.000 0.000 0.000 0.000 base_events.py:527(call_later)
5 0.000 0.000 0.000 0.000 base_events.py:548(call_at)
7 0.000 0.000 0.000 0.000 base_events.py:564(call_soon)
7 0.000 0.000 0.000 0.000 base_events.py:594(_call_soon)
2 0.000 0.000 0.000 0.000 base_futures.py:23(isfuture)
1 0.000 0.000 0.000 0.000 coroutines.py:268(iscoroutine)
6 0.000 0.000 0.001 0.000 demo2_1.py:11(display_date)
6 0.000 0.000 0.000 0.000 demo2_1.py:6(print_time)
5 0.000 0.000 0.000 0.000 events.py:114(cancel)
13 0.000 0.000 0.001 0.000 events.py:125(_run)
5 0.000 0.000 0.000 0.000 events.py:147(__init__)
5 0.000 0.000 0.000 0.000 events.py:192(cancel)
6 0.000 0.000 0.000 0.000 events.py:621(_get_running_loop)
2 0.000 0.000 0.000 0.000 events.py:632(_set_running_loop)
5 0.000 0.000 0.000 0.000 events.py:666(get_event_loop)
12 0.000 0.000 0.000 0.000 events.py:86(__init__)
5 0.000 0.000 0.000 0.000 futures.py:344(_set_result_unless_cancelled)
1 0.000 0.000 0.000 0.000 proactor_events.py:477(_loop_self_reading)
12 0.000 0.000 0.000 0.000 proactor_events.py:539(_process_events)
10 0.000 0.000 0.000 0.000 tasks.py:468(sleep)
1 0.000 0.000 0.000 0.000 tasks.py:507(ensure_future)
12 0.000 0.000 5.000 0.417 windows_events.py:417(select)
1 0.000 0.000 0.000 0.000 windows_events.py:429(recv)
1 0.000 0.000 0.000 0.000 windows_events.py:45(__init__)
1 0.000 0.000 0.000 0.000 windows_events.py:606(_register_with_iocp)
1 0.000 0.000 0.000 0.000 windows_events.py:616(_register)
12 0.000 0.000 5.000 0.417 windows_events.py:660(_poll)
5 0.000 0.000 0.000 0.000 {built-in method _heapq.heappop}
5 0.000 0.000 0.000 0.000 {built-in method _heapq.heappush}
1 0.000 0.000 0.000 0.000 {built-in method _overlapped.CreateIoCompletionPort}
12 5.000 0.417 5.000 0.417 {built-in method _overlapped.GetQueuedCompletionStatus}
1 0.000 0.000 0.000 0.000 {built-in method _thread.get_ident}
1 0.000 0.000 5.002 5.002 {built-in method builtins.exec}
2 0.000 0.000 0.000 0.000 {built-in method builtins.hasattr}
3 0.000 0.000 0.000 0.000 {built-in method builtins.isinstance}
24 0.000 0.000 0.000 0.000 {built-in method builtins.len}
5 0.000 0.000 0.000 0.000 {built-in method builtins.max}
3 0.000 0.000 0.000 0.000 {built-in method builtins.print}
12 0.000 0.000 0.000 0.000 {built-in method math.ceil}
3 0.000 0.000 0.000 0.000 {built-in method now}
7 0.000 0.000 0.000 0.000 {built-in method nt.getpid}
1 0.000 0.000 0.000 0.000 {built-in method sys.get_asyncgen_hooks}
2 0.000 0.000 0.000 0.000 {built-in method sys.set_asyncgen_hooks}
26 0.000 0.000 0.000 0.000 {built-in method time.monotonic}
1 0.000 0.000 0.000 0.000 {method 'WSARecv' of '_overlapped.Overlapped' objects}
2 0.000 0.000 0.000 0.000 {method 'add' of 'set' objects}
1 0.000 0.000 0.000 0.000 {method 'add_done_callback' of '_asyncio.Future' objects}
1 0.000 0.000 0.000 0.000 {method 'add_done_callback' of '_asyncio.Task' objects}
12 0.000 0.000 0.000 0.000 {method 'append' of 'collections.deque' objects}
5 0.000 0.000 0.000 0.000 {method 'cancelled' of '_asyncio.Future' objects}
12 0.000 0.000 0.000 0.000 {method 'clear' of 'list' objects}
1 0.000 0.000 0.000 0.000 {method 'disable' of '_lsprof.Profiler' objects}
1 0.000 0.000 0.000 0.000 {method 'discard' of 'set' objects}
1 0.000 0.000 0.000 0.000 {method 'done' of '_asyncio.Task' objects}
2 0.000 0.000 0.000 0.000 {method 'fileno' of '_socket.socket' objects}
13 0.000 0.000 0.000 0.000 {method 'popleft' of 'collections.deque' objects}
1 0.000 0.000 0.000 0.000 {method 'remove_done_callback' of '_asyncio.Task' objects}
1 0.000 0.000 0.000 0.000 {method 'result' of '_asyncio.Task' objects}
5 0.000 0.000 0.000 0.000 {method 'set_result' of '_asyncio.Future' objects}
脚本demo2_2.py运行结果如下：
2017-08-09 11:32:43.821214
2017-08-09 11:32:45.822848
2017-08-09 11:32:47.823607
22 function calls in 5.002 seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.000 0.000 5.002 5.002 <string>:1(<module>)
1 0.000 0.000 5.002 5.002 demo2_2.py:10(display_date)
3 0.000 0.000 3.002 1.001 demo2_2.py:6(print_time)
1 0.000 0.000 5.002 5.002 {built-in method builtins.exec}
3 0.000 0.000 0.000 0.000 {built-in method builtins.print}
3 0.000 0.000 0.000 0.000 {built-in method now}
5 5.002 1.000 5.002 1.000 {built-in method time.sleep}
4 0.000 0.000 0.000 0.000 {built-in method time.time}
1 0.000 0.000 0.000 0.000 {method 'disable' of '_lsprof.Profiler' objects}
Used: 5.006526947021484
总结： 在实际应用中，当我们需要使用协程方式来提过效率时，注意，需要使用异步非阻塞的形式来实现，否则就像time.sleep()，即使我们将它放在了协程实现中，也是达不到效率提高的，退化成了同步实现。
举例验证：
import time
import datetime
import tornado.ioloop
import tornado.web
import tornado.gen
class MainHandler(tornado.web.RequestHandler):
@tornado.gen.coroutine
def get(self):
yield tornado.gen.Task(self.blocksleep)
self.write("Hello, world")
@tornado.gen.coroutine
def blocksleep(self):
time.sleep(20)
return
def make_app():
return tornado.web.Application([
(r"/", MainHandler),
])
if __name__ == "__main__":
app = make_app()
app.listen(8888)
tornado.ioloop.IOLoop.current().start()
那么，当我们确实需要异步调用阻塞形式的代码时，有什么办法呢，可以使用线程, 还是上面的例子
import time
import datetime
import tornado.ioloop
import tornado.web
import tornado.gen
import tornado.concurrent
from concurrent.futures import ThreadPoolExecutor
class MainHandler(tornado.web.RequestHandler):
executor = ThreadPoolExecutor(10)
@tornado.gen.coroutine
def get(self):
future = ThreadPoolExecutor().submit(self.blocksleep)
yield tornado.gen.with_timeout(datetime.timedelta(10), future,
quiet_exceptions=tornado.gen.TimeoutError)
self.write("Hello, world")
@tornado.concurrent.run_on_executor
def blocksleep(self):
time.sleep(20)
return
def make_app():
return tornado.web.Application([
(r"/", MainHandler),
])
if __name__ == "__main__":
app = make_app()
app.listen(8888)
tornado.ioloop.IOLoop.current().start()
