Q:

Define instance attribute to store one of the two "constant" class attributes

I am still trying to understand how I can create an instance attribute on Employment_status to store one of the two constant attributes such as RESIGNED or CURRENT_EMPLOYEE.
So, when I defined my two constant class attributes, I can make my constructor to look like Employee(Employment_status, name, surname, number). The employment_status would take the argument from the Employment Status to change either "RESIGNED" or "CURRENT_EMPLOYEE", when the code is executed.
I have tried to performed my own coding, and would like to know if I am on the right track.
class Person:

    def __init__(self, name, surname, number):
    self.name = name
    self.surname = surname
    self.number = number

class Employee(Person):

    #class attribute
    def employment_status(object):
        employment_status = "CURRENT_EMPLOYEE"
        employment_status = "RESIGNED"

    #instance attributes
    def __init__(self, name, surname, number,employment_status):
        super().__init__(self,name,surname,number)
        self._employment_status = employment_status

A:

__init__ looks OK, assuming an Employee simply adds an employment status  to a Person.
It looks like it lays the ground work for employment_status to be a property, though, rather than an ordinary method.
@property
def employment_status(self):
    return self._employment_status

@employment_status.setter
def employment_status(self, status):
    if status not in ["CURRENT_EMPLOYEE", "RESIGNED"]:
        raise ValueError("Invalid status: {}".format(status))
    self._employment_status = status

Then you can get an employee's status:
>>> e = Employee("bob", "smith", 1, "CURRENT_EMPLOYEE")
>>> e.employment_status
"CURRENT_EMPLOYEE"

or change it
>>> e.employment_status = "RESIGNED"
>>> e.employment_status
"RESIGNED"
>>> e.employment_status = "foo"  # raises an exception
>>> e.employement_status
"RESIGNED"   # unchanged

Note that __init__ should use the setter as well, instead of assigning directly to _employment_status:
def __init__(self, name, surname, number,employment_status):
    super().__init__(self, name, surname, number)
    # not self._employment_status = ...
    self.employment_status = employment_status

