python 自定义方法获取最近几个月的日期比如最近三个月的日期就是；2019-07-01到2019-09-30

def calDate(self, months):
    pass
    today = datetime.date.today().strftime("%Y-%m-%d")
    cur_year = int(str(today)[0:4])

    cur_month = int(str(today)[5:7])
    # 最近一个月

    if cur_month -1 == 0:
        pass
        year = cur_year -1
        month = 12
    else:
        year = cur_year
        month = cur_month -1
    date = calendar.monthrange(year, month)

    # 最近 months 月数
    if cur_month -months == 0:
        pass
        latest_year = cur_year -1
        latest_month = 12
    else:
        latest_year = cur_year
        latest_month = cur_month -months
    latest_date = calendar.monthrange(year, month)
    return (str(year)+'-'+str(month)+'-'+str(date[1]), str(latest_year)+'-'+str(latest_month)+'-'+'01')