Edit: Licensed source can be found here.

The intent behind this class is to allow different game systems to run at their own clock rate. The physics integration rate should not be connected to the screen refresh rate, for instance. Instancing this class should allow for accurate, independent timing of separate systems.

Does this code meet that requirement?

An additional feature added while writing was access to the object's tps property, allowing for changes to operating rate during use.

from datetime import datetime

class Ticker:

    # 1,000,000; a one followed by six zeroes
    microseconds_per_second = 1000000

    def __init__(self, tps=1):
        self.tps = tps
        self._last_mark = 0
        self._accumulator = 0

    def tps(self):
        return self._tps

    def tps(self, ticks_per_second):
        assert int(ticks_per_second) == ticks_per_second
        assert 0 < ticks_per_second
        self._tps = ticks_per_second

    def last_mark(self):
        return self._last_mark

    def _microseconds_per_tick(self):
        return Ticker.microseconds_per_second / self.tps

    def tick(self):
        """Returns the number of unprocessed ticks.

        First call will initialize clock by setting first mark.
        This first call will return -1. All other calls will
        return an integer greater than or equal to zero.

        if not self.last_mark:
            # Set firt time mark and exit.
            self._last_mark = datetime.now()
            return -1

        # Get dt, the change in time, and update mark.
        next_mark = datetime.now()
        dt = next_mark - self._last_mark
        self._last_mark = next_mark

        # Increment accumulator by change in time:
        #   1) the seconds, which are converted to microseconds.
        #   2) the microseconds, which total less than one second.
        self._accumulator += (dt.seconds * Ticker.microseconds_per_second)
        self._accumulator += dt.microseconds

        # Drain full ticks from accumulator and return count.
        ticks_elapsed = 0
        while self._accumulator >= self._microseconds_per_tick:
            self._accumulator -= self._microseconds_per_tick
            ticks_elapsed += 1
        return ticks_elapsed

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.