# a person object: fields + behavior
# change: the tax method is now a computed attribute

class Person:
    def __init__(self, name, job, pay=0):
        self.name = name
        self.job  = job
        self.pay  = pay               # real instance data
    def __getattr__(self, attr):      # on person.attr
        if attr == 'tax':
            return self.pay * 0.30    # computed on access
        else:
            raise AttributeError      # other unknown names
    def info(self):
        return self.name, self.job, self.pay, self.tax