Class JSONFileConfigLoader

traitlets/config/loader.py:553–605

A JSON file loader for config Can also act as a context manager that rewrite the configuration file to disk on exit. Example:: with JSONFileConfigLoader('myapp.json','/home/jupyter/configurations/') as c: c.MyNewConfigurable.new_value = 'Updated'

class JSONFileConfigLoader(FileConfigLoader):
    """A JSON file loader for config

    Can also act as a context manager that rewrite the configuration file to disk on exit.

    Example::

        with JSONFileConfigLoader('myapp.json','/home/jupyter/configurations/') as c:
            c.MyNewConfigurable.new_value = 'Updated'

    """

    def load_config(self) -> Config:
        """Load the config from a file and return it as a Config object."""
        self.clear()
        try:
            self._find_file()
        except OSError as e:
            raise ConfigFileNotFound(str(e)) from e
        dct = self._read_file_as_dict()
        self.config = self._convert_to_config(dct)
        return self.config

    def _read_file_as_dict(self) -> dict[str, t.Any]:
        with open(self.full_filename) as f:
            return t.cast("dict[str, t.Any]", json.load(f))

    def _convert_to_config(self, dictionary: dict[str, t.Any]) -> Config:
        if "version" in dictionary:
            version = dictionary.pop("version")
        else:
            version = 1

        if version == 1:
            return Config(dictionary)
        else:
            raise ValueError(f"Unknown version of JSON config file: {version}")

    def __enter__(self) -> Config:
        self.load_config()
        return self.config

    def __exit__(self, exc_type: object, exc_value: object, traceback: object) -> None:
        """
        Exit the context manager but do not handle any errors.

        In case of any error, we do not want to write the potentially broken
        configuration to disk.
        """
        self.config.version = 1
        json_config = json.dumps(self.config, indent=2)
        with open(self.full_filename, "w") as f:
            f.write(json_config)


class PyFileConfigLoader(FileConfigLoader):