On 7/23/2014 6:43 AM, Saimadhav Heblikar wrote:
Hi,
The example in question is
https://docs.python.org/3/library/asyncio-task.html#example-hello-world-coroutine.
I'd like to learn the purpose of the statement
"yield from asyncio.sleep(2)" in that example.
In particular, I'd like to know if asyncio.sleep() is used as a
substitute for slow/time consuming operation, i.e. in real code,
whether there will be a real time consuming statement in place of
asyncio.sleep().
The context is
while True:
print('Hello')
yield from asyncio.sleep(3)
sleep is both itself, to shown to schedule something at intervals in a
non-blocking fashion, as well as a placefiller. The blocking equivalent
would use 'time' instead of 'yield from asyncio'. The following shows
the non-blocking feature a bit better.
import asyncio
@asyncio.coroutine
def hello():
while True:
print('Hello')
yield from asyncio.sleep(3)
@asyncio.coroutine
def goodbye():
while True:
print('Goodbye')
yield from asyncio.sleep(5.01)
@asyncio.coroutine
def world():
while True:
print('World')
yield from asyncio.sleep(2.02)
loop = asyncio.get_event_loop()
loop.run_until_complete(asyncio.wait([hello(), goodbye(), world()]))
Getting the same time behavior in a while...sleep loop requires
reproducing some of the calculation and queue manipulation included in
the event loop.
--
Terry Jan Reedy
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