首先设计一个point类，包含x，y两个属性，编写setxy()方法和showxy()输出方法。再设计一个circle类，继承自point类，包含一个属性r。编写setr方法和show-xyr()输出方法。，生成多个对象进行测试)

以下是Python实现：

class Point:
    def __init__(self, x=0, y=0):
        self.x = x
        self.y = y
    
    def setxy(self, x, y):
        self.x = x
        self.y = y
    
    def showxy(self):
        print(f"({self.x}, {self.y})")
    

class Circle(Point):
    def __init__(self, x=0, y=0, r=0):
        super().__init__(x, y)
        self.r = r
    
    def setr(self, r):
        self.r = r
    
    def showxyr(self):
        print(f"({self.x}, {self.y}), r={self.r}")
    

# 测试
c1 = Circle(1, 2, 3)
c1.showxyr()  # (1, 2), r=3
c1.setr(4)
c1.showxyr()  # (1, 2), r=4
c1.setxy(5, 6)
c1.showxyr()  # (5, 6), r=4

c2 = Circle()
c2.showxyr()  # (0, 0), r=0
c2.setxy(7, 8)
c2.showxyr()  # (7, 8), r=0
c2.setr(5)
c2.showxyr()  # (7, 8), r=5