Python 我的while函数没有返回任何值！我做错了什么

这是个新手

我有一个如下所示的数据帧：

currentMilestone            m2          SLA_M6          latedeliverydate            SLA_M3          earlypickupdate
            m2      2020-02-21      2020-02-18              2020-03-14          2020-02-09              2020-02-08
            m2      2020-02-21      2020-02-18              2020-02-14          2020-02-09              2020-02-08
            m2      2020-02-21      2020-02-18              2020-02-14          2020-02-09              2020-02-08
            m2      2020-02-21      2020-02-18              2020-02-14          2020-02-09              2020-02-08
            m1             NaT      2020-03-24              2020-02-14          2020-03-13              2020-03-18

def flag(data):

    while data.currentMilestone== 'm1'is True:

        if data.SLA_M6  > data.latedeliverydate:
            return 'R'
        elif (data.SLA_M3 != data.earlypickupdate) & (data.latedeliverydate <= data.SLA_M6):
            return 'A'

        elif (data.SLA_M3 == data.earlypickupdate) & (data.latedeliverydate >= data.earlypickupdate):
            return 'G'
        else:
            return None

我写过这样的文章：

currentMilestone            m2          SLA_M6          latedeliverydate            SLA_M3          earlypickupdate
            m2      2020-02-21      2020-02-18              2020-03-14          2020-02-09              2020-02-08
            m2      2020-02-21      2020-02-18              2020-02-14          2020-02-09              2020-02-08
            m2      2020-02-21      2020-02-18              2020-02-14          2020-02-09              2020-02-08
            m2      2020-02-21      2020-02-18              2020-02-14          2020-02-09              2020-02-08
            m1             NaT      2020-03-24              2020-02-14          2020-03-13              2020-03-18

def flag(data):

    while data.currentMilestone== 'm1'is True:

        if data.SLA_M6  > data.latedeliverydate:
            return 'R'
        elif (data.SLA_M3 != data.earlypickupdate) & (data.latedeliverydate <= data.SLA_M6):
            return 'A'

        elif (data.SLA_M3 == data.earlypickupdate) & (data.latedeliverydate >= data.earlypickupdate):
            return 'G'
        else:
            return None

当我运行我的函数时，我没有任何结果。。。我的意思是旗帜不能正常工作。所有行都设置为“无”

这里有什么问题吗？

用于此，因为

应用

效率很低：

import numpy as np

cond1 = data['currentMilestone'] == 'm1'

condlist = [
    (data['SLA_M6'] > data['latedeliverydate']) & cond1,
    (data['SLA_M3'] != data['earlypickupdate']) & (data['latedeliverydate'] <= data['SLA_M6']) & cond1,
    (data['SLA_M3'] == data['earlypickupdate']) & (data['latedeliverydate'] >= data['earlypickupdate']) & cond1
]

choicelist = ['R', 'A', 'G']

data['flag'] = np.select(condlist, choicelist, default=None)

---

您不应该在时使用

，因为您总是在每个条件下返回

。您如何调用该函数？返回值不会向数据帧添加列。一般提示：在条件表达式之后不需要

为True

。数据['flag']=data.apply（flag，axis=1）如果

data.currentMilestone='m1'

在首次调用函数时不为True，则while永远不会运行，您没有显式返回值，因此python会返回None。但是，您可能需要仔细检查您的逻辑和预期输出，因为这些条件的计算结果都不是

True

当然，我已经更新了数据，以便最后一行的计算结果为'True'