Get currency exchange updates from apilayer.net and generate a Unity notification on Ubuntu Desktop

currency_notify.py

import argparse
import os
import requests
import subprocess
import time

API_URL = 'http://apilayer.net/api'


class CheckAndNotify(object):

    def __init__(self, from_, to, interval, always):
        self.from_ = from_.upper()
        self.to = to.upper()
        self.interval = interval * 60  # minutes to seconds
        self.always = always
        self.access_key = os.environ.get('API_LAYER_KEY')
        self.last_rate = None
        self.currencies = []

    def get_default_params(self):
        return {'access_key': self.access_key}

    def validate_currencies(self):
        params = self.get_default_params()
        response = requests.get(f'{API_URL}/list', params=params)
        self.currencies = response.json()['currencies'].keys()
        return self.from_ in self.currencies and self.to in self.currencies

    def check_and_notify(self):
        params = self.get_default_params()
        params['currencies'] = ','.join([self.from_, self.to])
        while True:
            response = requests.get(f'{API_URL}/live', params=params)
            quotes = response.json()['quotes']
            rate = quotes[f'USD{self.to}']  / quotes[f'USD{self.from_}']
            message = f'1 {self.from_} = {round(rate, 4)} {self.to}'
            if not self.last_rate or self.always or self.last_rate != rate:
                self.last_rate = rate
                subprocess.run(['notify-send', message])
            time.sleep(self.interval)


if __name__ == '__main__':
    parser = argparse.ArgumentParser(description='Verify exchange rates and notify when target rates change.')
    parser.add_argument('from_', metavar='from', type=str, help='convert from this currency')
    parser.add_argument('to', metavar='to', type=str, help='convert to this currency')
    parser.add_argument('--interval', type=int, dest='interval', default=15,
                        help='how often to check for updates (default 15 min)')
    parser.add_argument('--always-notify', dest='always', action='store_true',
                        help='notify even if rate does not change (default False)')
    args = parser.parse_args()
    checker = CheckAndNotify(args.from_, args.to, args.interval, args.always)
    if checker.validate_currencies():
        checker.check_and_notify()
    else:
        print(f'{checker.from_} or {checker.to} is not a valid currency.'
              f' Please choose any of the following {list(checker.currencies)}')