def weekends_between(d1,d2):

    days_between = (d2-d1).days

    weekends, leftover = divmod(days_between,7)

    if leftover:

        start_day = (d2-timedelta(leftover)).isoweekday()

        end_day = start_day+leftover

        if start_day<=6 and end_day>6:

            weekends +=.5

        if start_day<=7 and end_day>7:

            weekends +=.5

    return weekends

参考使用：weekends_between(date(2004,10,1),date(2004,10,10))