# geometry.py

_angle_mode = 'd'

@property
def angle_mode(self):
    return self._angle_mode

@angle_mode.setter
def angle_mode(self, value):
    if value != 'd' or value != 'r':
        raise ValueError("ValueError: invalid mode: '{0}'".format(mode))
    self._angle_mode = value

class angle:
    def __init__(self, value, mode=None):
        if mode is None:
            mode = _angle_mode
        if mode == 'd':
            self.deg = value
            self.rad = math.radians(value)
        elif mode == 'r':
            self.rad = value
            self.deg = math.degrees(value)
        else:
            raise ValueError("ValueError: invalid mode: '{0}'".format(mode))

    def __repr__(self):
        if _angle_mode == 'd':
            return 'angle({0}deg)'.format(self.deg)
        elif _angle_mode == 'r':
            print(7)
            return 'angle({0}rad)'.format(self.rad)

# interpreter
>>> import geometry
>>> a, b = geometry.angle(72), geometry.angle(2, 'r')
>>> a, b
(angle(72deg), angle(114.59...deg))
>>> geometry.angle_mode = 'r'
>>> a, b
(angle(1.25...rad), angle(2rad))