Something

class Field(object):      __metaclass__ = DescMetaclass   def __init__(self, widget=None, required=True):      self.d={}      self.d['widget'] = widget      self.d['required'] = required         def render(self):      print self.desc      print self.dclass RegExpField(Field):      def __init__(self, widget=None, required=True, regexp=None, caseSensivity=False):      Field.__init__(self, widget=widget, required=required)      self.d['regexp'] = regexp      self.d['caseSensivity'] = caseSensivity   def main():        t=RegExpField('aaaa', regexp='.+', widget=123)    t.render()if __name__ == '__main__':    main()