class Person:
    def __init__(self, name, age):
        self.name = name
        self.set_age(age)
        self.children = []

    def set_age(self, age):
        if not isinstance(age, (float, int)):
            raise TypeError('age must be positive number')
        elif age < 0:
            raise ValueError('age must be positive number')

        self.__age = age

    def get_age(self):
        return self.__age

    def print_info(self):
        print(self.name, ',', self.__age)

joel = Person('Joel', 60)
print('name =', joel.name)
joel.print_info()
joel.set_age(-4)
print('age =', joel.get_age())
joel.print_info()