fill missing dates in dict.py

def date_range(first_date, second_date):
    """
    Returns range of dates between first and second date
    :type first_date: datetime.date
    :type second_date: datetime.date
    :return: list of dates
    """
    if first_date == second_date:
        return []
    elif first_date > second_date:
        return date_range(second_date, first_date)

    diff = second_date - first_date

    return [
        first_date + timedelta(days=x) for x in range(1, diff.days)
    ]


def fill_missing_dates(data, date_from, date_to, default_value=None):
    """
    Doplni dny ktera nejsou v datasetu.

    :param data: {datetime: value} - dictionary of daily stats for example
    :type data: dict
    :param date_from: datetime
    :type date_from: datetime.date
    :param date_to: datetime
    :type date_to: datetime.date
    :param default_value: value to use in
    :return: dictionary with filled dates
    """

    # get real date range which might differ from input data
    min_date = min([date_from, min(data.keys())]) if date_from else min(data.keys())
    max_date = max([date_to, max(data.keys())]) if date_to else min(data.keys())

    full_day_range = date_range(min_date, max_date)
    missing_days = set(full_day_range) - set(data.keys())

    for missing_day in missing_days:
        data[missing_day] = default_value

    return data