sleep-until 1.1

Sleep until a specific time

sleep_until

This module provides a function sleep_until(deadline_seconds), which is like time.sleep(), but it sleeps until the specified time of the system clock as returned by time.time(). This can be used, for example, to schedule events at a specific timestamp obtained from datetime.datetime.timestamp().

See the notes in time.sleep() on the behavior when interrupted and on accuracy. Additionally, because this function uses the system clock as a reference (CLOCK_REALTIME on Unix), this means the reference clock is adjustable and may jump backwards. Limited testing has shown that sleep_until should still work in a predictable fashion (either returning immediately if the system clock is adjusted back, or sleeping until the specified wall-clock time if the system clock is adjusted forwards), however, this behavior can currently not be guaranteed by this module, so be sure to test the behavior on your system if you expect to be making adjustments to the system clock while sleep_until is running (including via a background NTP service).

• On POSIX systems, clock_nanosleep(2) is used, so this must be available, along with the appropriate tools to compile the module.
• On Windows, SetWaitableTimerEx is used, in combination with CREATE_WAITABLE_TIMER_HIGH_RESOLUTION if available. Precompiled "wheels" for CPython are available on PyPI (wheels for other OSes are not provided because it is not guaranteed that clock_nanosleep(2) is available there).
• On Mac OS X, at the time of writing, clock_nanosleep is still not available, so the module currently does not build there.

Here is how one might implement a loop that executes at a specific interval:

from time import time
from sleep_until import sleep_until

interval_s = 1

# using "int" here to start on a full second
next_s = int(time()) + interval_s
while True:
    # calculate the next wake-up time and sleep until then
    now_s = time()
    # if the user's code takes longer than the interval, skip intervals
    while next_s < now_s:
        next_s += interval_s
    sleep_until(next_s)

    # run any user-specified code here
    print(time())