class foo:
  def __init__(self, **kwargs):
    if 'a' in kwargs:
      self.a = kwargs['a']
    else:
      self.a = 0

class bar(foo):
  def __init__(self, **kwargs):
    super().__init__()
    if 'x' in kwargs:
      self.x = kwargs['x']
    else:
      self.x = 23

# b and y are undefined, but my classes use kwargs - what is the best practice for validating / parsing dynamic arguments?
test = bar(b=1,y=24)