parser = argparse.ArgumentParser(description='Currency convertor. Before using the program read the instruction -h')
parser.add_argument('--amount', type=float, help='The amount you want to convert.')
parser.add_argument('--input_currency', help='Currency to conver. The format is three letters example. USD')
parser.add_argument('--output_currency', type=str, help='The target currency')

args = parser.parse_args()
currency.append('EUR')
rates.append(1)
if args.input_currency == None:
    print('Error: Wrong format or currency not suported. The format is three letters. example: USD')
    print('Supported currencies:', currency)
    quit()
elif len(args.input_currency) != 3:
    print('Error: Wrong format. The format is three letters. example:', currency)
    quit()
else:
    d = dict(zip(currency, rates))
    rate_i = float(d.get(args.input_currency.upper()))

    if args.output_currency == None:
        del d[(args.input_currency.upper())]
        output= {key:((float(value) / rate_i) * args.amount) for key, value in d.items()}
    else:
        if len(args.output_currency) != 3:
            print('Error: Wrong format. The format is three letters. example:', currency)
            quit()
        else:
            rate_o = float(d.get(args.output_currency.upper()))
            output= {args.output_currency: (rate_o / rate_i) * args.amount}
result={
    "input": {
              "amount": args.amount,
              "currency": args.input_currency
    },

    "output": output
}
print(json.dumps(result, indent=4))