8.2.1 The function property

The special function property links an attribute to such a getter, setter, and deleter method. It might also be used to assign a documentation string to an attribute:

attribute = property(fget = get_attr, fset = set_attr, 
                     fdel = del_attr, doc = string)

We continue with the previous example with a setter method and consider the class Triangle again. If the following statement is included in the definition of this class, the command tr.B = <something> invokes the setter method set_B:

B = property(fget = get_B, fset = set_B, fdel = del_B, 
             doc = ’The point B of a triangle’)

Let's modify the Triangle class accordingly:

class Triangle:
    def __init__(self, A, B, C):
        self._A = array(A)
        self._B = array(B)
        self._C = array(C)
        self._a = self._C - self._B
        self._b = self._C - self._A
        self._c = self._B - self._A
    def area(self):
        return abs(cross(self._c...