title: Error: Namespace has no attribut first_parameter
body: <p>I try making a loan calculator for a project with <code>argparse</code> but i can't make it work</p>
  <pre class="lang-py prettyprint-override"><code>parser = argparse.ArgumentParser()
  parser.add_argument('--type', '--first_parameter', choices=['annuity', 'diff'], help='Incorrect parameters')
  parser.add_argument('--principal', '--second_parameter')
  parser.add_argument('--payment', '--third_parameter')
  parser.add_argument('--periods', '--fourth_parameter')
  parser.add_argument('--interest', '--fifth_parameter')
  args = parser.parse_args()
  all_parameter = [args.first_parameter, args.second_parameter, args.third_parameter, args.fourth_parameter,
                   args.fifth_parameter]
  </code></pre>