configuration module with attribute-like option access and json file data storage

config.py

# -*- coding: utf-8 -*-
"""Configuration class storing data as jsonfile.
Written for micropython which has no configparser module, but can be
used on regular python as well. The goal is to make a configuration class
that is simpler and less painful to use than ConfigParser."""

try:
    # micropython module
    import ujson as json
except ImportError:
    # "regular" python module
    import json


class Config(dict):
    """Configuration class using a JSON file to read and write settings.
    Options are accessed and assigned as attributes. For example:

    config.foo is equivalent to config['foo']
    config.foo = 'bar' is equivalent to config['foo'] = 'bar'

    NB. if attribute is absent, KeyError is raised."""
    # these two assignments allow us to read/write dictionary items
    # using object attribute protocol
    __getattr__ = dict.__getitem__
    __setattr__ = dict.__setitem__

    def __init__(self, filename=None, *args, **kwargs):
        if filename is None:
            raise ValueError('You MUST specify a filename as the first arg!')

        # store the filename in a low-level object's dict
        # so that clear() doesn't erase it
        self.__dict__['filename'] = filename

        # fill the underlying dictionary with keys and values
        super().__init__(*args, **kwargs)

        try:
            # read conffile contents, then update with arguments,
            # so that arguments have precedence over file
            self.load(self.filename)
            super().update(*args, **kwargs)
        except FileNotFoundError:
            # create a new conffile
            self.save()

    def save_as(self, filename):
        """Save the current config to file"""
        with open(filename, 'w+') as jsonfile:
            contents = json.dumps(self)
            jsonfile.write(contents)

    def save(self):
        """Save the current config to self.filename"""
        self.save_as(self.filename)

    def load(self, filename, clear=False):
        """Load configuration data from a specified file"""
        with open(filename, 'r') as jsonfile:
            raw = jsonfile.read()
            contents = json.loads(raw)
            if clear:
                super().clear()
            super().update(**contents)

    def reload(self):
        """Load self.filename and overwrite all unsaved changes"""
        self.load(self.filename, clear=True)

    def update(self, *args, **kwargs):
        """Update the configuration data and save it to file"""
        # args = dict-like objects; kwargs = key-value mappings
        super().update(*args, **kwargs)
        self.save()