human
I am working on the file "Descriptors and Properties.ipynb".
The first task is:
So that's a lot of fancy theory, but what might be a practical application of the above.  Suppose we want a circle to let us modify its radius at will, and to treat area as an ordinary attribute nonetheless...
Can you write Python program for it?

Here might be a practical application of the above?
assistant
#Here might be a practical application of the above.

import math

class Circle:
    
    def __init__(self, r):
        self.radius = r
    
    @property
    def area(self):
        return self.radius ** 2 * math.pi
    
    def __repr__(self):
        return "Circle({})".format(self.radius)
    
the_circle = Circle(1)
print(the_circle) # triggers __repr__ in the absence of __str__
print("Area of the circle: {:f}".format(the_circle.area))
the_circle.radius = 2
print("Area of the circle: {:f}".format(the_circle.area))