class Person(User):

    MALE = 'M'
    FEMALE = 'F'

    GENDER = (
        (MALE, 'Male'),
        (FEMALE, 'Female'),
    )

    birth_date = models.DateField()

    gender = models.CharField(max_length = 1, choices = GENDER)

class SignupForm(ModelForm):
    MALE = 'M'
    FEMALE = 'F'

    GENDER = (
        (MALE, 'Male'),
        (FEMALE, 'Female'),
    )

    thisYear = date.today().year

    YEARS = [thisYear - year for year in range(100)]

    password = forms.CharField(widget = forms.PasswordInput(), min_length=5, max_length = 128)

    birth_date = forms.DateField(widget=extras.SelectDateWidget(years = YEARS), initial='1990-01-01')

    gender = forms.ChoiceField(choices = GENDER, initial='M')

    class Meta:
        model = Person
        exclude = ('last_name', 'is_staff', 'is_active', 'is_superuser', 'last_login', 'date_joined', 'user_permissions', 'groups', 'attraction' )

        #all fields in this list will map to a specific model attribute and will be comitted to the database
        fields = ('username', 'password', 'first_name', 'email', 'gender', 'birth_date')

user = models.OneToOneField(User)
blah =
.
.

if form.is_valid():
    user = User.objects.create_user(username = form.cleaned_data['username'],
                                    email = form.cleaned_data['email'],
                                    password = form.cleaned_data['password'],
                                    )