config.py

import json
import os

DEFAULT_CONFIG = {
    'api_key': 'your_api_key',
    'api_secret': 'your_api_secret',
    'base_currency': 'USD',
    'timeout': 30
}

class ConfigLoader:
    def __init__(self, config_file='config.json'):
        self.config_file = config_file
        self.config = self.load_config()

    def load_config(self):
        if os.path.exists(self.config_file):
            with open(self.config_file, 'r') as file:
                return {**DEFAULT_CONFIG, **json.load(file)}
        return DEFAULT_CONFIG

    def get(self, key, default=None):
        return self.config.get(key, default)

if __name__ == '__main__':
    loader = ConfigLoader()
    print(loader.get('api_key'))