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Python: time.sleep(n) would sleep much longer than n seconds?

0 votes
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I'm writing some scripts with python, and I found sometimes, when I try to use time.sleep(1) to sleep 1 sec, it would actually sleep for 9/10 secs or even longer.

From python document, I saw this:

time.sleep(secs)
....
"Also, the suspension time may be longer than requested by an arbitrary amount because of the scheduling of other activity in the system."

So, my question: under what kind of condition, time.sleep would suspend longer time than expected?

posted Jun 18, 2014 by anonymous

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1 Answer

+1 vote

There are several reasons the sleep time is always described as "at least" that long. Firstly, your process will always sleep for some multiple of the kernel's internal task switching resolution. That doesn't explain why time.sleep(1) will sleep for nine seconds, but if you try this, you'll see that at work:

for i in range(1000): time.sleep(0.001)

In theory, that should be the same as time.sleep(1), right? Well, no.On my systems it sleeps for 2-3 seconds at least, which suggests that there's a minimum of 2-3 milliseconds of sleep time. And it could easily sleep for a lot longer than that.

answer Jun 18, 2014 by Sidharth
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