def icon_mapping(icon, size):
    """
    https://darksky.net/dev/docs has this to say about icons:
    icon optional
    A machine-readable text summary of this data point, suitable for selecting
    an icon for display. If defined, this property will have one of the
    following values: clear-day, clear-night, rain, snow, sleet, wind, fog,
    cloudy, partly-cloudy-day, or partly-cloudy-night. (Developers should
    ensure that a sensible default is defined, as additional values, such as
    hail, thunderstorm, or tornado, may be defined in the future.)

    Based on that, this method will map the Dark Sky icon name to the name of
    an icon in this project.
    """
    if icon == 'clear-day':
        icon_path = 'icons/{}/clear.png'.format(size)
    elif icon == 'clear-night':
        icon_path = 'icons/{}/nt_clear.png'.format(size)
    elif icon == 'rain':
        icon_path = 'icons/{}/rain.png'.format(size)
    elif icon == 'snow':
        icon_path = 'icons/{}/snow.png'.format(size)
    elif icon == 'sleet':
        icon_path = 'icons/{}/sleet.png'.format(size)
    elif icon == 'wind':
        icon_path = 'icons/alt_icons/{}/wind.png'.format(size)
    elif icon == 'fog':
        icon_path = 'icons/{}/fog.png'.format(size)
    elif icon == 'cloudy':
        icon_path = 'icons/{}/cloudy.png'.format(size)
    elif icon == 'partly-cloudy-day':
        icon_path = 'icons/{}/partlycloudy.png'.format(size)
    elif icon == 'partly-cloudy-night':
        icon_path = 'icons/{}/nt_partlycloudy.png'.format(size)
    else:
        icon_path = 'icons/{}/unknown.png'.format(size)

    # print(icon_path)
    return icon_path