Get options in Python from both JSON files and command line arguments

This is the Python version of another article, "Getting options in Ruby from both JSON files and command line arguments" (https://qiita.com/aikige/items/014139c0b1ae70139477). With the increasing use of Python these days, I'll share the results of my thoughts on how to write the same thing in Python.

Basic concept

Collect options in one object. Example: class Options
Read the options from the JSON file when creating the object. Example: opt = Options ('some.json') reads options from a JSON file.
Use the object's attribute to access options. Example: You can access it like opt.option_1.
Use Argparse to capture command line arguments.
The optional object has a method that fetches the value from the result generated by Arguparse. Example: Import with something like opt.import_opt (options).

Implementation example

https://gist.github.com/aikige/470f4ef93753638cc3a18d62e195eb19

#!/usr/bin/env python

import json
import os

class Options:
    OPTS = { 'option_1': 'bool', 'option_2': 'str' }

    def __init__(self, filename='config.json'):
        if (os.path.exists(filename)):
            with open(filename) as f:
                self.import_dict(json.load(f))

    def import_attr(self, key, value):
        if (value is None):
            return
        if (isinstance(value, eval(self.OPTS[key]))):
            setattr(self, key, value)
        else:
            raise ValueError("invalid type")

    def import_dict(self, d):
        for key in self.OPTS.keys():
            if (key in d.keys()):
                self.import_attr(key, d[key])

    def import_opt(self, args):
        for key in self.OPTS.keys():
            if (hasattr(args, key)):
                self.import_attr(key, getattr(args, key))

if __name__ == '__main__':
    import argparse

    opt = Options()
    print(vars(opt))

    parser = argparse.ArgumentParser()
    parser.add_argument('-1', '--option_1', action='store_true', default=None)
    parser.add_argument('-2', '--option_2', type=str)
    args = parser.parse_args()
    print(vars(args))
    opt.import_opt(args)
    print(vars(opt))

Main differences from Ruby version

Unlike Ruby, Python has a bool type, so it's relatively easy to incorporate type determination (import_attr).
In case of Python, Arrgparse is used for option analysis, so JSON analysis and argument analysis methods are not unified. , Slightly redundant.
In case of Python, it seems a little difficult to make attribute read-only, so I omitted it.