Currency converter using Yahoo API

currency.py

from decimal import Decimal
import json
import urllib

def convert(from_val, from_cur, to_cur):
    """
    currency codes: http://en.wikipedia.org/wiki/ISO_4217
    """
    url = "https://query.yahooapis.com/v1/public/yql"
    q_tmpl = 'select * from yahoo.finance.xchange where pair in ("%s%s")'
    p = {'q': q_tmpl % (from_cur, to_cur),
         'env': 'store://datatables.org/alltableswithkeys',
         'format': 'json', }
    qry_str = urllib.urlencode(p)
    resp = urllib.urlopen("?".join([url, qry_str]))
    j = json.loads(resp.read())
    rate = j['query']['results']['rate']['Rate']
    to_val = Decimal(str(from_val)) * Decimal(rate)
    return to_val.quantize(Decimal('0.00'))

if __name__ == '__main__':
    print convert(1, 'EUR', 'USD')