import math

class Circle:

    def __init__(self, radius):
        self.__radius = radius  #

    def get_area(self):
        return math.pi * self.__radius ** 2

    def get_perimeter(self):
        return 2 * math.pi * self.__radius

    # getter method for radius attribute

    def get_radius(self):
        return self.__radius

    # setter method for radius attribute

    def set_radius(self, radius):
        if not isinstance(radius, int):
            print("Error: ", radius, "is not an int")
            return
        self.__radius = radius

c = Circle(6)

# print(c.__radius)

c.get_radius()  # get the initial value of __radius attribute

# c.set_radius("a radius")  # trying to set invalid value

print(c.get_radius())  # value of __radius attribute is still same

print(c.set_radius(10)) # this time operation succeeds
print(c.get_radius())  #  get the new value of __radius attribute