timer.py

from timeit import default_timer
from datetime import timedelta


class Timer:
    """Timer class.

    Examples:
        >>> import time
        >>> t = Timer()
        >>> t.start()
        >>> time.sleep(1)
        >>> t.stop()
        >>> t.interval > 0.8 and t.interval < 1.2
        True
        >>> with Timer() as t:
        ...   time.sleep(1)
        >>> t.interval > 0.8 and t.interval < 1.2
        True
        >>> "Time elapsed {}".format(t) #doctest: +ELLIPSIS
        'Time elapsed 1...'
    """

    def __init__(self):
        self._timer = default_timer
        self._interval = 0
        self.running = False

    def __enter__(self):
        self.start()
        return self

    def __exit__(self, *args):
        self.stop()

    def __str__(self):
        return "{:0.4f}".format(self.interval)

    def start(self):
        """Start the timer."""
        self.init = self._timer()
        self.running = True

    def stop(self):
        """Stop the timer. Calculate the interval in seconds."""
        self.end = self._timer()
        try:
            self._interval = self.end - self.init
            self.running = False
        except AttributeError:
            raise ValueError(
                "Timer has not been initialized: use start() or the contextual form with Timer() as t:"
            )

    @property
    def interval(self):
        if self.running:
            raise ValueError("Timer has not been stopped, please use stop().")
        else:
            return self._interval