Pandas - 更改数据框的对齐方式

Question

我创建了一个数据框:

In [1]: import pandas as pd 

In [2]: import numpy as np

In [3]: df = pd.DataFrame({ 'Student_ID':['001','002','003','004','005'],
                'Amy'   : ['Amy',np.nan,np.nan,np.nan,'Amy'],
                'Brian' : [np.nan,'Brian',np.nan,np.nan,np.nan],
                'Cat'   : [np.nan,np.nan,np.nan,'Cat',np.nan]},columns=['Student_ID','Amy','Brian','Cat']) 


In  [4]:df
Out [4]:
    Student_ID  Amy Brian   Cat
0          001  Amy   NaN   NaN
1          002  NaN Brian   NaN
2          003  NaN   NaN   NaN
3          004  NaN   NaN   Cat
4          005  Amy   NaN   NaN

接下来我想返回一个只有两列的数据框，Student_ID 和 Name。如何转换为以下精确代码？

In [5]: df
Out[5]: 
  Student_ID    Name    
0        001     Amy    
1        002   Brian    
2        003     NaN    
3        004     Cat
4        005     Amy    

Answer 1

你可以使用点

df.iloc[:,1:].notna().dot(df.columns[1:])
Out[78]: 
0      Amy
1    Brian
2         
3      Cat
4      Amy
dtype: object
#df['name']=df.iloc[:,1:].notna().dot(df.columns[1:])

或者bfill

df.iloc[:,1:].bfill(1).iloc[:,0]
Out[82]: 
0      Amy
1    Brian
2      NaN
3      Cat
4      Amy