Last day of previous months

ultimo.py

import datetime,calendar

def ultimo(num=3,today=None):
    """return a list of datetime.date with the last day of num previous months"""
    if today is None:
        today = datetime.date.today()
    return [datetime.date(y,m,calendar.monthrange(y,m)[1]) for \
            m,y in (((today.month - i -1) % 12+1, today.year + \
            ((today.month - i -1) // 12)) for i in range(num+1,0,-1))]