Return a dateint range of the week the given dateint belongs to.

    Arguments
    ---------
    dateint : int
        An integer object decipting a specific calendaric day; e.g. 20161225.
    first_day : str, default 'Monday'
        The first day of the week.

    Returns
    -------
    iterable
        An iterable of dateint representing all days of the week the given
        dateint belongs to.

def dateint_week_by_dateint(dateint, first_day='Monday'):
    """Return a dateint range of the week the given dateint belongs to.

    Arguments
    ---------
    dateint : int
        An integer object decipting a specific calendaric day; e.g. 20161225.
    first_day : str, default 'Monday'
        The first day of the week.

    Returns
    -------
    iterable
        An iterable of dateint representing all days of the week the given
        dateint belongs to.
    """
    weekday_ix = dateint_to_weekday(dateint, first_day)
    first_day_dateint = shift_dateint(dateint, -weekday_ix)
    last_day_dateint = shift_dateint(first_day_dateint, 6)
    return dateint_range(first_day_dateint, last_day_dateint)