import math


class Circle:
    def __init__(self, x, y, r):
        self.x = x
        self.y = y
        self.r = r

    def area(self):
        return math.pi * self.r ** 2


c = Circle(0, 0, 1)
print(c.x)
print(c.y)
print(c.r)
c.r = 2
print(c.r)
print(c.area())

import math


class Circle:
    def __init__(self, x, y, r):
        self.x = x
        self.y = y
        self.set_r(r)

    def area(self):
        return math.pi * self.r ** 2

    def set_r(self, r):
        if r < 0:
            raise ValueError("Radius should be nonnegative")
        self._r = r

    def get_r(self):
        return self._r


c = Circle(0, 0, 1)
print(c.x)
print(c.y)
c.set_r(2)
print(c.get_r())
c.set_r(-1)

import math


class Circle:
    def __init__(self, x, y, r):
        self.x = x
        self.y = y
        self.r = r

    def area(self):
        return math.pi * self.r ** 2

    @property
    def r(self):
        return self._r

    @r.setter
    def r(self, r):
        if r < 0:
            raise ValueError("Radius should be nonnegative")
        self._r = r


c = Circle(0, 0, 1)
print(c.x)
print(c.y)
c.r = 2
print(c.r)
c.r = -1

import math


class Circle:
    def __init__(self, x, y, r):
        self.x = x
        self.y = y
        self.r = r

    def area(self):
        return math.pi * self.r ** 2

    @property
    def r(self):
        return self._r

    @r.setter
    def r(self, r):
        if r < 0:
            raise ValueError("Radius should be nonnegative")
        self._r = r

    def __str__(self):
        return 'Circle: x={}, y={}, r={}'.format(self.x, self.y, self.r)

    def __repr__(self):
        return 'Circle(x={}, y={}, r={})'.format(self.x, self.y, self.r)

    def __lt__(self, other):
        return self.r < other.r

    def __add__(self, other):
        return Circle(self.x + other.x, self.y + other.y, self.r + other.r)


c = Circle(0, 0, 1)
print(c)
print(repr(c))
c2 = Circle(x=0, y=0, r=1)
print(c2)
print(c < c2)
print(c + c2)