BASE_URL = "http://api.nbp.pl/api/exchangerates/rates/a"
code = 'GBP'
start_date = '2018-02-10'
end_date = '2019-01-20'

def get_values(code: str, start_date: str, end_date: str) -> dict:
    """ Function takes currency 'code', 'start_date' and 'end_date' of searching data
        and package rates into the dictionary"""
    url = f"{BASE_URL}/{code}/{start_date}/{end_date}/?format=json"
    response = requests.get(url)
    rates = json.loads(response.text)
    return {rate["effectiveDate"]: rate["mid"] for rate in rates["rates"]}

values_dictionary = get_values(code, start_date, end_date)


-------- ZWRACANY BŁAD W KONSOLI --------

Traceback (most recent call last):
  File "nbp.py", line 72, in <module>
    main()
  File "nbp.py", line 67, in main
    values_dictionary = get_values(code, start_date, end_date)
  File "nbp.py", line 33, in get_values
    rates = json.loads(response.text)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/json/__init__.py", line 348, in loads
    return _default_decoder.decode(s)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/json/decoder.py", line 340, in decode
    raise JSONDecodeError("Extra data", s, end)
json.decoder.JSONDecodeError: Extra data: line 1 column 5 (char 4)