def sin_values(period=360):
    """
    Provides an infinite source of values representing a sine wave (from -1 to
    +1) which repeats every *period* values. For example, to produce a "siren"
    effect with a couple of LEDs that repeats once a second::

        from gpiozero import PWMLED
        from gpiozero.tools import sin_values, scaled, inverted
        from signal import pause

        red = PWMLED(2)
        blue = PWMLED(3)

        red.source_delay = 0.01
        blue.source_delay = red.source_delay
        red.source = scaled(sin_values(100), 0, 1, -1, 1)
        blue.source = inverted(red)

        pause()

    If you require a different range than -1 to +1, see :func:`scaled`.
    """
    angles = (2 * pi * i / period for i in range(period))
    for a in cycle(angles):
        yield sin(a)