Currency converter

converter.py

from json import load
from re import compile

def validate(query):
    # amount, start currency, end currency, .dp
    preg = compile(r"(\d+\.?\d*?)\s*?([a-zA-Z]{3})\s*?([a-zA-Z]{3})\s*?(\d*?)")
    if preg.match(query):
        return [i.upper() for i in preg.split(query) if len(i) > 0]
    return False

def load_exchange_rates(l="rates.json"):
    # load exchange rates
    with open("rates.json", "r") as rates_file:
        json = load(rates_file) 
    rates = json["rates"]
    rates["base"] = json["base"]
    return rates

def main():
    query = validate(input("> "))
    if query:
        query[0] = float(query[0]) # float value
        if len(query) > 3: # if .dp is set float it
            query[3] = int(query[3])
        else:
            query.append(5) # else set to default
        rates = load_exchange_rates()
        if query[1] in rates and query[2] in rates:
            usd = query[0] / rates[query[1]]
            result = round(usd * rates[query[2]], query[3])
            print(result, query[2])
        else:
            print("Both currencies must be valid")
    else:
        print("Invalid query")

if __name__ == '__main__':
    while True:
        main()

rates.json

{
  "disclaimer": "Exchange rates are provided for informational purposes only, and do not constitute financial advice of any kind. Although every attempt is made to ensure quality, NO guarantees are given whatsoever of accuracy, validity, availability, or fitness for any purpose - please use at your own risk. All usage is subject to your acceptance of the Terms and Conditions of Service, available at: https://openexchangerates.org/terms/",
  "license": "Data sourced from various providers with public-facing APIs; copyright may apply; resale is prohibited; no warranties given of any kind. All usage is subject to your acceptance of the License Agreement available at: https://openexchangerates.org/license/",
  "timestamp": 1388682062,
  "base": "USD",
  "rates": {
    "AED": 3.67306,
    "AFN": 56.139451,
    "ALL": 102.287,
    "AMD": 407.754002,
    "ANG": 1.78898,
    "AOA": 97.997351,
    "ARS": 6.540306,
    "AUD": 1.120609,
    "AWG": 1.789825,
    "AZN": 0.7841,
    "BAM": 1.430071,
    "BBD": 2,
    "BDT": 77.70406,
    "BGN": 1.43028,
    "BHD": 0.375078,
    "BIF": 1546.279267,
    "BMD": 1,
    "BND": 1.26805,
    "BOB": 6.91737,
    "BRL": 2.391847,
    "BSD": 1,
    "BTC": 0.0012875567,
    "BTN": 62.138538,
    "BWP": 8.789733,
    "BYR": 9538.85,
    "BZD": 1.99615,
    "CAD": 1.063279,
    "CDF": 922.310333,
    "CHF": 0.89784,
    "CLF": 0.022705,
    "CLP": 528.632002,
    "CNY": 6.073266,
    "COP": 1936.766667,
    "CRC": 501.155998,
    "CUP": 22.682881,
    "CVE": 80.026899,
    "CZK": 20.03053,
    "DJF": 177.99246,
    "DKK": 5.450412,
    "DOP": 42.64074,
    "DZD": 78.440181,
    "EEK": 11.662575,
    "EGP": 6.957495,
    "ERN": 14.981325,
    "ETB": 19.16174,
    "EUR": 0.73159,
    "FJD": 1.880114,
    "FKP": 0.608239,
    "GBP": 0.608239,
    "GEL": 1.74795,
    "GHS": 2.33732,
    "GIP": 0.608239,
    "GMD": 38.192,
    "GNF": 6973.65,
    "GTQ": 7.85657,
    "GYD": 204.238749,
    "HKD": 7.753801,
    "HNL": 20.2659,
    "HRK": 5.579015,
    "HTG": 43.6305,
    "HUF": 217.701201,
    "IDR": 12157.7,
    "ILS": 3.486491,
    "INR": 62.18248,
    "IQD": 1162.985033,
    "IRR": 24749.667967,
    "ISK": 115.418999,
    "JEP": 0.608239,
    "JMD": 106.122499,
    "JOD": 0.707782,
    "JPY": 104.967401,
    "KES": 86.779971,
    "KGS": 49.1893,
    "KHR": 3992.583516,
    "KMF": 358.79217,
    "KPW": 900,
    "KRW": 1053.011685,
    "KWD": 0.282482,
    "KYD": 0.827492,
    "KZT": 154.517001,
    "LAK": 8032.366602,
    "LBP": 1503.7,
    "LKR": 130.755301,
    "LRD": 80.779049,
    "LSL": 10.55737,
    "LTL": 2.522992,
    "LVL": 0.512675,
    "LYD": 1.24033,
    "MAD": 8.209011,
    "MDL": 13.03114,
    "MGA": 2242.766667,
    "MKD": 44.98572,
    "MMK": 987.466275,
    "MNT": 1642.666667,
    "MOP": 7.99525,
    "MRO": 291.621002,
    "MTL": 0.683602,
    "MUR": 30.22293,
    "MVR": 15.37172,
    "MWK": 432.66,
    "MXN": 13.10622,
    "MYR": 3.287194,
    "MZN": 29.94395,
    "NAD": 10.58889,
    "NGN": 159.14,
    "NIO": 25.49832,
    "NOK": 6.126554,
    "NPR": 99.38224,
    "NZD": 1.21844,
    "OMR": 0.385071,
    "PAB": 1,
    "PEN": 2.80293,
    "PGK": 2.495964,
    "PHP": 44.46257,
    "PKR": 105.43966,
    "PLN": 3.045351,
    "PYG": 4605.50332,
    "QAR": 3.641591,
    "RON": 3.27826,
    "RSD": 83.72113,
    "RUB": 33.04588,
    "RWF": 678.12102,
    "SAR": 3.750735,
    "SBD": 7.191706,
    "SCR": 12.0626,
    "SDG": 5.70085,
    "SEK": 6.480564,
    "SGD": 1.265604,
    "SHP": 0.608239,
    "SLL": 4347.166667,
    "SOS": 1120.0417,
    "SRD": 3.283333,
    "STD": 17906.667333,
    "SVC": 8.76193,
    "SYP": 141.197499,
    "SZL": 10.58763,
    "THB": 32.89692,
    "TJS": 4.774225,
    "TMT": 2.8501,
    "TND": 1.6504,
    "TOP": 1.859269,
    "TRY": 2.167617,
    "TTD": 6.41698,
    "TWD": 29.93288,
    "TZS": 1577.4,
    "UAH": 8.24798,
    "UGX": 2531.233333,
    "USD": 1,
    "UYU": 21.22256,
    "UZS": 2202.183317,
    "VEF": 6.294525,
    "VND": 21112,
    "VUV": 96.665,
    "WST": 2.325016,
    "XAF": 479.897111,
    "XAG": 0.05075862,
    "XAU": 0.00081578,
    "XCD": 2.70156,
    "XDR": 0.650863,
    "XOF": 480.673999,
    "XPF": 87.04516,
    "YER": 215.045,
    "ZAR": 10.63664,
    "ZMK": 5253.075255,
    "ZMW": 5.518167,
    "ZWL": 322.355006
  }
}