python计算时间差

    last_time = last.device_createtime    now_time = datetime.datetime.now()    diff = now_time - last_time    if diff.days > 0:        last_createtime = str(diff.days) + ' Days Ago'    else:        m, s = divmod(diff.seconds, 60)        h, m = divmod(m, 60)        if h > 0:            last_createtime = str(h) + ' Hours Ago'        elif m > 0:            last_createtime = str(m) + ' mins Ago'        else:            last_createtime = 'Just Now'