[Tutor] calling setters of superclasses

[Gregory, Matthew]

Hi all,

Consider the following classes where PositiveX should constrain the attribute _x to be positive and SmallX should further constrain the attribute _x to be less than 10.

class PositiveX(object):
    def __init__(self):
        self._x = 1
    @property
    def x(self):
        return self._x
    @x.setter
    def x(self, val):
        if val < 0:
            raise ValueError('Negatives not allowed')
        self._x = val

class SmallX(PositiveX):
    @property
    def x(self):
        return self._x
    @x.setter
    def x(self, val):
        # How do I call the superclass' @x.setter
        super(SmallX, self).__setattr__('x', val)
        if val > 10:
            raise ValueError('Big values not allowed')
        self._x = val

I thought I could call the superclass setter first to ensure the value was positive, but I'm getting an infinite recursion.  I also tried:

  super(SmallX, self).x = val

but I get this:

  AttributeError: 'super' object has no attribute 'x'  

I'm fully confused and, therefore, likely doing something stupid.

thanks, matt