Python ISO week for date

gistfile1.py

import datetime

def week_for_date(target):
    """Given a target date, return a start and end for that date's ISO week.

    The returned tuple includes two datetime.date's, (start, end):
    start: midnight on the first day of the ISO week containing the target
    end: midnight on the first day following the ISO week containing the target

    Note that the end date represents the first date _not_ in the target week,
    but rather an upper bound, so the following must always be true:

    start <= any date/time in the target's ISO week < end
    """
    year, week, dow = target.isocalendar()
    start = target.date() - datetime.timedelta(dow - 1)  # ISO days of week are 1-based
    end = start + datetime.timedelta(7)
    return (start, end)