def last_n_months(n=12, ending=None):
    """Return a list of tuples of the first/last day of the month
    for the last N months
    """
    from datetime import date
    from dateutil.rrule import rrule, MONTHLY
    from dateutil.relativedelta import relativedelta

    if not ending:
        ending = date.today()

    # set the ending date to the last day of the month
    ending = ending + relativedelta(months=+1, days=-ending.day)

    # starting is the first day of the month N months ago
    starting = ending - relativedelta(months=n, day=1)

    months = list(rrule(MONTHLY, bymonthday=(1, -1), dtstart=starting,
                        until=ending))

    # we return pairs of dates like this: (1st day of month, last day of month)
    months = zip(months[::2], months[1::2])

    return months

>>> from datetime import date, timedelta

    # get last two months as a degenerate example
    >>> l2n = last_n_months(2, ending=date(2012, 01, 01))
    >>> map(lambda x: [x[0].year, x[0].month, x[0].day], l2n)
    [[2011, 11, 1], [2011, 12, 1], [2012, 1, 1]]
    >>> map(lambda x: [x[1].year, x[1].month, x[1].day], l2n)
    [[2011, 11, 30], [2011, 12, 31], [2012, 1, 31]]

    >>> l24n = last_n_months(24, ending=date(2012,03,16))
    >>> len(l24n) # inclusive of current month
    25

    # every tuple starts with the first day of the month
    >>> all(x[0].day == 1 for x in l24n)
    True

    # every tuple ends with the last day of the month
    >>> all((x[1] +timedelta(days=1)).month != x[1].month for x in l24n)
    True

    # every tuple is the same month
    >>> all(x[0].month == x[1].month for x in l24n)
    True

def last_n_months(n=12, ending=None):
    """Return a list of tuples of the first/last day of the month
    for the last N months
    """
    from datetime import date
    from dateutil.rrule import rrule, MONTHLY
    from dateutil.relativedelta import relativedelta

if not ending:

ending = date.today()

    # set the ending date to the last day of the month
    ending = ending + relativedelta(months=+1, days=-ending.day)

# starting is the first day of the month N months ago
    starting = ending - relativedelta(months=n, day=1)

    months = list(rrule(MONTHLY, bymonthday=(1, -1), dtstart=starting,
                        until=ending))

    # we return pairs of dates like this: (1st day of month, last day of month)
    months = zip(months[::2], months[1::2])

    return months