有办法在 subclass 中修改 parent class 的方法，使其返回某个变量吗？（ parent class 的该方法无返回值）

# parent class
class A(object):
    # ... bala bala ...
    def test(self, url):
        # ... bala bala ...
        rsp = self.http.send(url=url)
        rsp = json.loads(rsp.content)
        self._session = self._session_type(rsp['a'], rsp['b'])

# subclass
class B(A):
    def test(self, url):
        # ... bala bala ...
        rsp = self.http.send(url=url)
        rsp = json.loads(rsp.content)
        self._session = self._session_type(rsp['a'], rsp['b'])
        self._xx = rsp['xx']

如果 A.test 有将 rsp 返回的话，那 subclass 就只需要

class B(A):
    def test(self, url):
        rsp = super(self.__class__, self).test(url)
        self._xx = rsp['xx']

所以...是否有办法可以让 parent class 的 test 方法返回 rsp 呢？（排除修改 parent class 源码的方法）

Supplement 1 · Jun 28, 2017

2楼的方法测试可行，实际代码片段测试，tracert 的覆盖方法会比复制父类代码的覆盖方法慢上9~10倍（timerit repeat number = 100000）

import sys

# parent class
class A(object):
    # ... bala bala ...
    def test(self, url):
        # ... bala bala ...
        rsp = self.http.send(url=url)
        rsp = json.loads(rsp.content)
        self._session = self._session_type(rsp['a'], rsp['b'])

# subclass
class B(A):
    def test(self, url):
        _locals = {}

        def tracert(frame, event, arg):
            if event == 'return':
                _locals.update(frame.f_locals.copy())

        sys.setprofile(tracert)
        
        try:
            super(self.__class__, self).test(url)
        finally:                       
            sys.setprofile(None)       
        rsp = _locals['rsp']
        self._xx = rsp['xx']

6 replies • 2017-06-29 07:41:59 +08:00