How to call a variable outside a validate() function which is inside the FlaskForm class

class RegistrationForm(FlaskForm):

    def __init__(self, *args, **kwargs):
        super(RegistrationForm, self).__init__(*args, **kwargs)
        self.total_travel_km = None

    def validate_home_address(self, home_address):
        user_loc = locator.geocode(home_address.data)
        user_coords = (user_loc.latitude, user_loc.longitude)
        one_way = geopy.distance.geodesic(tco_coords, user_coords).km
        total_travel_km = one_way * 4
        if total_travel_km < self.car_range.data:
            raise ValidationError('You live too close to work')
        # all good save the total travel in the form
        self.total_travel_km = total_travel_km

class RegistrationForm(FlaskForm):

    def __init__(self, *args, **kwargs):
        super(RegistrationForm, self).__init__(*args, **kwargs)
        self.total_travel_km = None
        self.required_car_range = kwargs.get('required_car_range', 400)

    def validate_car_range(self, car_range):
        if car_range.data > self.required_car_range:
            raise ValidationError('Your car range does not meet our requirements')

@app.route("/register", methods=['POST', 'GET'])
def register():
    form = RegistrationForm(required_car_range=600)
    if form.validate_on_submit():
        user = User(car_range=form.car_range.data, home_address=form.home_address.data,
                    car_travel_km=form.total_travel_km)
        db.session.add(user)
        db.session.commit()