Python的奇怪报错

def cust_period(value, op="days", op_period=0, base_dt=None):
    value_list = value.tolist()
    while "-1" in value_list:
        value_list.remove("-1")
    if len(value_list) != 0:
        if not base_dt:
            max_dt = max(value_list)
        else:
            max_dt = base_dt

        if op == "years":
            end_dt = (datetime.datetime.strptime(max_dt, "%Y/%m/%d %H:%M") + relativedelta(years=-op_period)).strftime("%Y/%m/%d %H:%M")
        elif op == "months":
            end_dt = (datetime.datetime.strptime(max_dt, "%Y/%m/%d %H:%M") + relativedelta(months=-op_period)).strftime("%Y/%m/%d %H:%M")
        elif op == "weeks":
            end_dt = (datetime.datetime.strptime(max_dt, "%Y/%m/%d %H:%M") + relativedelta(weeks=-op_period)).strftime("%Y/%m/%d %H:%M")
        elif op == "days":
            end_dt = (datetime.datetime.strptime(max_dt, "%Y/%m/%d %H:%M") + relativedelta(days=-op_period)).strftime("%Y/%m/%d %H:%M")
        else:
            print("Wrong operation unit of time!")
            exit()
        period = list(value.values >= end_dt)
        return period
    else:
        return [True]*len(value.tolist())

data1自然流量['date_time']=data1['date_time'].astype('datetime64')
agg_2m = data1自然流量[data1自然流量['date_time'].dt.month !=12].groupby('date_time')['date','全部自然流量']
agg_2m = agg_2m.apply(lambda x: x[cust_period(x['date'], "months", 2)])
agg_2m = agg_2m.groupby("date_time")["全部自然流量"].agg(["sum"])

为什么到最后一步时只报错KeyError: 'date_time'

img


这是读取的原文件，请帮忙看看，谢谢！

因为在定义函数cust_period时，对参数value调用了tolist()方法，将其转换为列表。在最后一步中，agg_2m已经不是原来的数据框，而是一个经过计算的新数据框，它没有'date_time'这一列。所以在最后一步中会报错KeyError: 'date_time'。