appliance.py

PRICE_KWH = 0.11  # TODO get list of prices per country


class ApplianceCost:

    def __init__(self, name, wattage, price_kwh=PRICE_KWH):
        self.name = name
        self.wattage = wattage
        self.price_kwh = price_kwh
        self._minutes = []  # log minutes

    @property
    def cost(self):
        hours_used = sum(self._minutes)/60
        cost = self.wattage * hours_used / 1000 * self.price_kwh
        return round(float(cost), 2)

    def consume(self, minutes):
        if not isinstance(minutes, int):
            raise ValueError('Please use int for minutes')
        self._minutes.append(minutes)


if __name__ == '__main__':
    # examples from:
    # https://energy.gov/energysaver/estimating-appliance-and-home-electronic-energy-use

    k = ApplianceCost('kettle', 1500)
    use = 365 * 60
    k.consume(use)
    assert k.cost == 60.23
    print(k.cost)

    s = ApplianceCost('shredder', 360)
    use = 52 * 15
    s.consume(use)
    assert s.cost == 0.51
    print(s.cost)