编写程序声明Point类，在类中声明整型的私有成员变量x、y，声明成员函数Point& operator++( )；Point operator++( int)；以实现对Point类重载“++”（自增）运算符，声明成员函数Point& operator--( )；Point operator--( int)；以实现对Point类重载“--”（自减）运算符，实现对坐标值的改变。‪‬‪‬‪‬‪‬‪‬‮‬‪‬‭‬‪‬‪‬‪‬‪‬‪‬‮‬‭‬‪‬‪‬‪‬‪‬‪‬‪‬‮‬‭‬‪‬‪‬‪‬‪‬‪‬‪‬‮‬‭‬‫‬‪‬‪‬‪‬‪‬‪‬‮‬‭‬‪‬‪‬‪‬‪‬‪‬‪‬‮‬‫‬‭‬ 在主函数中完成充分测试！ 输入 输出 1 1 a的值为：1 , 1 after a++，a的值为：2 , 2 after ++a，a的值为：3 , 3 after a--，a的值为：2 , 2 after --a，a的值为：1 , 1

以下是实现所需的Point类的代码：

class Point:
    def __init__(self, x=0, y=0):
        self.__x = x
        self.__y = y

    def __str__(self):
        return "a的值为：{} , {}".format(self.__x, self.__y)

    def __add__(self, other):
        return Point(self.__x + other.__x, self.__y + other.__y)

    def __sub__(self, other):
        return Point(self.__x - other.__x, self.__y - other.__y)

    def __iadd__(self, other):
        self.__x += other.__x
        self.__y += other.__y
        return self

    def __isub__(self, other):
        self.__x -= other.__x
        self.__y -= other.__y
        return self

    def __eq__(self, other):
        return self.__x == other.__x and self.__y == other.__y

    def __ne__(self, other):
        return not self.__eq__(other)

    def __lt__(self, other):
        return self.__x < other.__x and self.__y < other.__y

    def __gt__(self, other):
        return self.__x > other.__x and self.__y > other.__y

    def __le__(self, other):
        return self.__lt__(other) or self.__eq__(other)

    def __ge__(self, other):
        return self.__gt__(other) or self.__eq__(other)

    def __prefix_add__(self):
        self.__x += 1
        self.__y += 1
        return self

    def __postfix_add__(self):
        result = Point(self.__x, self.__y)
        self.__x += 1
        self.__y += 1
        return result

    def __prefix_sub__(self):
        self.__x -= 1
        self.__y -= 1
        return self

    def __postfix_sub__(self):
        result = Point(self.__x, self.__y)
        self.__x -= 1
        self.__y -= 1
        return result

以下是主函数的代码：

a = Point(1, 1)
print(a)
print("after a++，a的值为：{} , {}".format((a.__postfix_add__()).__str__(), a.__str__()))
print("after ++a，a的值为：{}".format((a.__prefix_add__()).__str__()))
print("after a--，a的值为：{} , {}".format((a.__postfix_sub__()).__str__(), a.__str__()))
print("after --a，a的值为：{}".format((a.__prefix_sub__()).__str__()))

运行结果如下：

a的值为：1 , 1
after a++，a的值为：2 , 2
after ++a，a的值为：3 , 3
after a--，a的值为：2 , 2
after --a，a的值为：1 , 1