python - 如何根据 Pandas 另一列中的条件生成具有值的新列

Question

我有一个如下所示的数据框，我需要生成一个名为“Comment”的新列，对于指定的值，它应该显示为“Fail”

输入:

        Tel    MC             WT

        AAA    Rubber         9999
        BBB    Tree           0
        CCC    Rub            12
        AAA    Other          20
        BBB    Same           999
        DDD    Other-Same     70 

尝试代码:

          df.loc[(df[WT] == 0 | df[WT] == 999 | df[WT] == 9999 | df[WT] == 99999),'Comment'] = 'Fail'

错误:

         AttributeError: 'str' object has no attribute 'loc'

预期输出:

       Tel    MC             WT      Comment
       AAA    Rubber         9999    Fail
       BBB    Tree           0       Fail
       CCC    Rub            12
       AAA    Other          20
       BBB    Same           999     Fail
       DDD    Other-Same     70

Answer 1

使用Series.isin对于测试成员，不匹配的值为 NaNs:

df.loc[df['WT'].isin([0, 999,9999,99999]),'Comment'] = 'Fail'
print (df)
   Tel          MC    WT Comment
0  AAA      Rubber  9999    Fail
1  BBB        Tree     0    Fail
2  CCC         Rub    12     NaN
3  AAA       Other    20     NaN
4  BBB        Same   999    Fail
5  DDD  Other-Same    70     NaN

如果需要分配Fail 和空值使用numpy.where :

df['Comment'] = np.where(df['WT'].isin([0, 999,9999,99999]), 'Fail', '')
print (df)
   Tel          MC    WT Comment
0  AAA      Rubber  9999    Fail
1  BBB        Tree     0    Fail
2  CCC         Rub    12        
3  AAA       Other    20        
4  BBB        Same   999    Fail
5  DDD  Other-Same    70