Convenience class for sleeping in a loop at a specified rate (based on rospy.Rate)

rate.py

from time import time_ns, sleep


class Rate(object):
    """
    Convenience class for sleeping in a loop at a specified rate
    """

    def __init__(self, hz, reset=True):
        """
        Constructor.
        @param hz: hz rate to determine sleeping
        @type  hz: float
        @param reset: if True, timer is reset when time moved backward. [default: True]
        @type  reset: bool
        """
        self.last_time = time_ns()
        self.sleep_dur = 1e9 / float(hz)
        self._reset = reset

    def _remaining(self, curr_time):
        """
        Calculate the time remaining for rate to sleep.
        @param curr_time: current time
        @type  curr_time: L{Time}
        @return: time remaining
        @rtype: L{Time}
        """
        # detect time jumping backwards
        if self.last_time > curr_time:
            self.last_time = curr_time

        # calculate remaining time
        elapsed = curr_time - self.last_time
        return self.sleep_dur - elapsed

    def remaining(self):
        """
        Return the time remaining for rate to sleep.
        @return: time remaining
        @rtype: L{Time}
        """
        curr_time = time_ns()
        return self._remaining(curr_time)

    def sleep(self):
        """
        Attempt sleep at the specified rate. sleep() takes into
        account the time elapsed since the last successful
        sleep().

        @raise ValueError: if time is set backwards
        """
        curr_time = time_ns()
        try:
            sleep(1e-9 * self._remaining(curr_time))
        except ValueError:
            if not self._reset:
                raise
            self.last_time = time_ns()
            return
        self.last_time = self.last_time + self.sleep_dur

        # detect time jumping forwards, as well as loops that are
        # inherently too slow
        if curr_time - self.last_time > self.sleep_dur * 2:
            self.last_time = curr_time