multithreading - Interrupt signals awake Python process from sleeping and continue where it left off? -

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the following code print out current time every 5 seconds, , handles keyboard interrupt signals int_handler.

from signal import * import time datetime import datetime   def int_handler(*args):     print 'interrupted'  signal(sigint, int_handler)  while true:     print datetime.now()     time.sleep(5)

however, every time press ctrl-c print out current time immediately, , continue running. 

2016-06-28 18:17:19.441574 2016-06-28 18:17:24.446659 2016-06-28 18:17:29.451759 2016-06-28 18:17:34.452328 ^cinterrupted 2016-06-28 18:17:37.244227 ^cinterrupted 2016-06-28 18:17:37.692217 ^cinterrupted 2016-06-28 18:17:38.236343 ^cinterrupted 2016-06-28 18:17:38.572194 2016-06-28 18:17:43.577122 2016-06-28 18:17:48.577242

it seems interruption awakes process sleeping, handler gets executed, , somehow gets while loop again.

can explain me why? thanks!

from documentation of sleep():

the actual suspension time may less requested because caught signal terminate sleep() following execution of signal’s catching routine.

https://docs.python.org/3/library/time.html#time.sleep

so describe happening: after handling signal in signal handler execution continues after sleep, last expression in while-loop.

hence in order sleep approximately 5 seconds ignoring interruptions you'd have store time before sleep , check on waking enough has passed, or sleep more.


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