import abc
from abc import ABCMeta


class Person(object, metaclass=ABCMeta):
    def __init__(self, first, last, age):
        self.firstname = first
        self.lastname = last
        self.age = age

    @abc.abstractmethod
    def change_info(self):
        pass


class Employee(Person):
    def __init__(self, first, last, age, staffnum):
        super(Employee, self).__init__(first, last, age)
        self.staffnumber = staffnum

    def change_info(self, firstname, lastname, age, staffnum):
        self.firstname = firstname
        self.lastname = lastname
        self.age = age
        self.staffnum = staffnum


y = Employee("Homer", "Simpson", 28, "1007")
y.change_info("Harry", "Potter", 20, "322")
print(y.firstname)