operator.py

import math

class Circle:

    def __init__(self, radius):
	    self.__radius = radius
		
    def setRadius(self, radius):
	    self.__radius = radius
	
    def getRadius(self):
	    return self.__radius
		
    def area(self):
	    return math.pi * self.__radius ** 2
		
    def __add__(self, another_circle):
	    return Circle(self.__radius + another_circle.__radius)
		
    def __sub__(self, another_circle):
	    return Circle(self.__radius - another_circle.__radius)
	
c1 = Circle(8)
print(c1.getRadius())

c2 = Circle(10)
print(c2.getRadius())

c3 = c1 + c2
print(c3.getRadius())

c3 = c2 - c1
print(c3.getRadius())