从列中获取一个元素，如果该元素等于某个元素，则将其放入python中的另一列中

假设我有这样一个数据帧：

        full_path                     
0   C:\Users\User\Desktop\Test1\1.txt 
1   C:\Users\User\Desktop\ABC\1.txt 
2   C:\Users\User\Desktop\Test2\1.txt 
3   C:\Users\User\Desktop\Test1\1.txt 
4   C:\Users\User\Desktop\ABCD\1.txt 
5   C:\Users\User\Desktop\Test2\1.txt 

我想检查路径的第5个元素是否等于test1和Test2，并创建如下列：

        full_path                             folder 
0   C:\Users\User\Desktop\Test1\1.txt         Test1
1   C:\Users\User\Desktop\ABC\1.txt          
2   C:\Users\User\Desktop\Test2\1.txt         Test2
3   C:\Users\User\Desktop\Test1\1.txt         Test1
4   C:\Users\User\Desktop\ABCD\1.txt          
5   C:\Users\User\Desktop\Test2\1.txt         Test2

我尝试了这个命令

df['folder']=df[“full\u path”].str.rsplit（“\\”）.str[4]

，但它给出了以下输出：

        full_path                             folder 
0   C:\Users\User\Desktop\Test1\1.txt         Test1
1   C:\Users\User\Desktop\ABC\1.txt           ABC
2   C:\Users\User\Desktop\Test2\1.txt         Test2
3   C:\Users\User\Desktop\Test1\1.txt         Test1
4   C:\Users\User\Desktop\ABCD\1.txt          ABCD 
5   C:\Users\User\Desktop\Test2\1.txt         Test2

---

我不希望在文件夹列中显示不是Test1和Test2的文件夹

您可以在以下位置使用Numpy：

import numpy as np

df['folder'] = np.where(df['full_path'].str.contains('Test'),
                        df['full_path'].str.rsplit('\\').str[4],
                        np.nan
                       )

输出：

                            full_path    folder
0   C:\Users\User\Desktop\Test1\1.txt     Test1
1     C:\Users\User\Desktop\ABC\1.txt       NaN
2   C:\Users\User\Desktop\Test2\1.txt     Test2
3   C:\Users\User\Desktop\Test1\1.txt     Test1
4    C:\Users\User\Desktop\ABCD\1.txt       NaN
5   C:\Users\User\Desktop\Test2\1.txt     Test2