Returns the cross rates for selected currency

exchange.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# Version: 0.1a1
# Introducing the API: https://swea.riksbank.se/sweaWS/docs/api/index.htm
# Series for web services: https://www.riksbank.se/en-gb/statistics/search-interest--exchange-rates/web-services/series-for-web-services/

import datetime

import zeep

def get_cross_rates(currency, start, end=None, delta=0, reverse=False):

    result = {}

    if end is None:
        end = start
    seriesid1 = 'SEK{}PMI'.format(currency.upper())
    if isinstance(start, str):
        start = datetime.datetime.strptime(start, '%Y-%m-%d').date()
    start = start - datetime.timedelta(days=delta)
    if isinstance(end, str):
        end = datetime.datetime.strptime(end, '%Y-%m-%d').date()
    end = end + datetime.timedelta(days=delta)
    client = zeep.Client('http://swea.riksbank.se/sweaWS/wsdl/sweaWS.wsdl')
    CrossRequestParameters = {'aggregateMethod': 'D',
                              'crossPair': {'seriesid1': seriesid1,
                                            'seriesid2': 'SEK'},
                              'datefrom': start,
                              'dateto': end,
                              'languageid': 'en'}
    groups = client.service.getCrossRates(CrossRequestParameters).groups
    data = zeep.helpers.serialize_object(groups[0])
    series = data['series']
    rows = series[reverse]['resultrows']
    for row in rows:
        result[row['date']] = row['value']
    return result

# Example: '1 SEK = ? USD' 4th of June 2019
#result = get_cross_rates('USD', '2019-06-04')

# Example: '1 SEK = ? USD' beetwen 4th and 5th of June 2019
#result = get_cross_rates('USD', '2019-06-04', '2019-06-05')

# Example: '1 USD = ? SEK' beetwen 4th and 5th of June 2019
#result = get_cross_rates('USD', '2019-06-04', '2019-06-05', reverse=True)

# Example: '1 SEK = ? USD' beetwen 3rd and 5th of June 2019
#result = get_cross_rates('USD', '2019-06-04', delta=1)