python 类的继承

class Event(object):
    SIGNAL = 'SIGNAL'
    ORDER='ORDER'
    def __init__(self, route, args):
        self.data = {
            'route': route,
            'data': args
        }
    def __str__(self):
        return "route: %s\nargs: %s" % (self.data['route'], self.data['data'])
    @property
    def route(self):
        return self.data['route']
    @property
    def args(self):
        """"""
        return self.data['data']
class SignalEvent(Event):
    """ 由策略函数产生的交易信号事件。 """
    def __init__(self, orders):
        super(SignalEvent, self).__init__(Event.SIGNAL, orders)
    @property
    def orders(self):
        return self.data['data']
orders={'units':100,'direction':'buy','symbol':'USDJPY'}
a=SignalEvent(orders)
a
a.orders
a.args
a.route