def QA_util_stamp2datetime(timestamp):
    """
    datestamp转datetime
    pandas转出来的timestamp是13位整数 要/1000
    It’s common for this to be restricted to years from 1970 through 2038.
    从1970年开始的纳秒到当前的计数 转变成 float 类型时间 类似 time.time() 返回的类型
    :param timestamp: long类型
    :return: 类型float
    """
    try:
        return datetime.datetime.fromtimestamp(timestamp)
    except Exception as e:
        # it won't work ??
        try:
            return datetime.datetime.fromtimestamp(timestamp / 1000)
        except:
            try:
                return datetime.datetime.fromtimestamp(timestamp / 1000000)
            except:
                return datetime.datetime.fromtimestamp(timestamp / 1000000000)