Sleep for exact time in python

Question

I need to wait for about 25ms in one of my functions. Sometimes this function is called when the processor is occupied with other things and other times it has the processor all to itself.

I've tried time.sleep(.25) but sometimes its actually 25ms and other times it takes much longer. Is there a way to sleep for an exact amount of time regardless of processor availability?

Answer 1

Because you're working with a preemptive operating system, there's no way you can guarantee that your process will be able to have control of the CPU in 25ms.

If you'd still like to try, it would be better to have a busy loop that polls until 25ms has passed. Something like this might work:

import time
target_time = time.clock() + 0.025
while time.clock() < target_time:
    pass

Answer 2

0.25 seconds are 250 ms, not 25. Apart from this, there is no way to wait for exactly 25 ms on common operating systems – you would need some real-time operating system.