hookenv.py 文件源码

def load_previous(self, path=None):
        """Load previous copy of config from disk.

        In normal usage you don't need to call this method directly - it
        is called automatically at object initialization.

        :param path:

            File path from which to load the previous config. If `None`,
            config is loaded from the default location. If `path` is
            specified, subsequent `save()` calls will write to the same
            path.

        """
        self.path = path or self.path
        with open(self.path) as f:
            self._prev_dict = json.load(f)
        for k, v in copy.deepcopy(self._prev_dict).items():
            if k not in self:
                self[k] = v