class Hub:
    '''A collection of sensors in a physical location.'''

    def __delitem__(self, key):
        del self.sensors[key]

    def __getitem__(self, key):
        return self.sensors[key]

    def __init__(self, name, *sensors):
        self.name = name
        self.sensors = {}
        self.add_sensors(*sensors)

    def __setitem__(self, key, value):
        self.sensors[key] = value

    def __str__(self):
        return str(self.name)

    def add_sensor(self, sensor):
        sname = sensor.name
        self.sensors[sname] = sensor

    def add_sensors(self, *sensors):
        for s in sensors:
            self.add_sensor(s)


class Sensor:
    def __init__(self, name, mincrit=0, minwarn=0, maxwarn=100, maxcrit=100):
        self.name = name
        self.maxcrit = maxcrit
        self.maxwarn = maxwarn
        self.mincrit = mincrit
        self.minwarn = minwarn

    @property
    def value(self):
        '''Get the present value of the sensor.'''
        return (self.mincrit + self.maxcrit) / 2

    def __str__(self):
        return str(self.name)

if __name__ == '__main__':
    at = Sensor('airtemp')
    wt = Sensor('watertemp')
    hub = Hub('hubba-hubba', at, wt)

    print("Current air temperature:", hub['airtemp'].value)