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Introductory python-changing classes properties

  1. Feb 8, 2012 #1
    1. The problem statement, all variables and given/known data

    Code (Text):
    class Person(object):
       """Defines a person with dob (date-of-birth, string), gender
       (two-value string), name (string) and age (integer)."""
       def __init__(self, dob, gender, name):
        assert (isinstance(dob,str) and dob.isdigit()
        and len(dob) == 8), 'dob is not in the format yyyymmdd'
        assert (gender == "Male" or
        gender == "Female"), 'gender can be only "Male" or "Female"'
        super(Person, self).__init__()
        self._dob = dob
        self.gender = gender
        self.name = name
    make a bold step and allow an already existing person object to change its gender
    (Male to Female or Female to Male, but no other) by redefining the gender attribute
    as a property with getter and setter aspects (the gender value should be stored
    in a hidden variable, for example called _gen). Once redefined, the person object
    gender change will be controlled:
    Code (Text):
    >>> p.gender
    'Male'
    >>> p.gender = 'Female'
    This is going to cost you!
    >>> p.gender
    'Female'
    >>> p.gender = 'Androgyne'
    You cannot become Androgyne (no such thing)

    3. The attempt at a solution
    i made a method within the class definition. when called, the method will check the gender then print the line. but i don't know how to do this without defining a method. and i also don't get the hidden variable thing, because it can be accessed out side the class anyways. lastly, what is a class property? how do i change class attributes into class properties? there is this property() function, but i'm not really sure its relevancy.

    Code (Text):
        def set_gender(self,g):
            assert g=='Male' or g=='Female','no such thing'
            print 'this is going to cost you!'
            self.gender=g
     
  2. jcsd
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