new_simple_step2.py

class _CelsiusConverter(TemperatureConverter):
    """
    Concrete implementation of temperature converted which converts from Kelvin
    into Celsius degrees.
    """

    symbol = '°C'

    def _convert(self, value):
        return value - 273.15


class _FahrenheitConverter:
    """
    Concrete implementation of temperature converter which converts from Kelvin
    into Fahrenheit degrees.
    
    Note that this class does not directly inherit base class, but is
    registered as derived class using ABCMeta.register method. Though in this
    case, there is no a default implementation of `format` method and `name`
    property.
    """

    symbol = '°F'

    def _convert(self, value):
        return value * 9./5 - 459.67

    def format(self, value):
        return '%.2f (%s)' % (self._convert(value), self.symbol)

    @property
    def name(self):
        return 'FahrenheitConverter'


TemperatureConverter.register(_FahrenheitConverter)