代理模式，在调用真实方法之前后分别执行所需的操作。

class RealRequest(object):
    def __init__(self):
        super().__init__()

    def request(self):
        print("request")


class Proxy(object):
    def __init__(self, real_request):
        self.real_request = real_request

    def request(self):
        self.before_request()
        self.real_request.request()
        self.after_request()

    def before_request(self):
        print("before_request")

    def after_request(self):
        print("after_request")


def main():
    real_request = RealRequest()
    proxy = Proxy(real_request)
    proxy.request()


if __name__ == '__main__':
    main()