class Person:
    def __init__(self, name, age, birthdate, children):
        self.name = name
        self.set_age(age)
        self.__set_birthdate(birthdate)
        self.__children = list()
        for c in children:
            self.new_child(c)
    
    def print_children(self):
        print("children are:")
        for c in self.__children:
            print('    child =', c.name)

    def new_child(self, child):
        if not isinstance(child, Person):
            raise TypeError('child must be a Person')

        self.__children.append(child)
    
    def set_age(self, age):
        if not isinstance(age, int):
            raise TypeError('age must be a positive int')
        elif age < 0:
            raise ValueError('age must be a positive int')
        
        self.__age = age
    
    def get_age(self):
        return self.__age

    def incr_age(self, val):
        self.__age += 1

    age = property(get_age, set_age)
    age_incr = property(get_age, incr_age)

    def __set_birthdate(self, birthdate):
        #validate thate birthdate is a valid birthdate
        if not isinstance(birthdate, tuple):
            raise TypeError('birthdate must be a tuple with 3 values')
        elif len(birthdate) != 3:
            raise ValueError('birthdate must be a tuple with 3 values')

        #format is (year, month, day)
        self.__BIRTHDATE = birthdate

    def get_birthdate(self):
        return self.__BIRTHDATE

    birthdate = property(get_birthdate)

    def get_home_planet(self):
        return "Earth"

    home_planet = property(get_home_planet)
    
    def set_name(self, name):
        self.name = name

    def get_name(self):
        return self.name

    def __eq__(x, y):
        '''two people are equal if their names and birthdates are the same'''
        if isinstance(y, Person):
            if x.name.lower() == y.name.lower() and x.__BIRTHDATE == y.__BIRTHDATE:
                return True
            else:
                return False
        elif isinstance(y, tuple) and len(y) == 3:
            if x.name.lower() == y[0].lower() and x.__BIRTHDATE == y[2]:
                return True
            else:
                return False
        else:
            raise TypeError("Person can only be compared to another person.")

alice = Person("Alice", 6, (2009, 11, 4), [])
try:
    joel = Person("Joel", 65, (1954, 11, 4), [alice])
    joel.new_child(joel)
except:
    print('err')
print('name =', joel.name)
joel.print_children()


joel.new_child(alice)

joels_children.append(alice)
joels_children.append(1)
joels_children.append(13.5)
joels_children.append((2009, 11, 4))

joel.print_children()