Pandas dataframe中的变换

Question

I have a data frame (2 columns: Text and HD/TTL) in the format below:

    Text  HD/TTL
     ABC   HD
     DEF   
     GHI   HD
     JKL
     MNO    
     PQR   HD

I want it transformed into a new data frame (with 2 columns: HD and Text) as:

    HD  Text
    HD  ABC\nDEF
    HD  GHI\nJKL\nMNO
    HD  PQR\n

where \n is the new line between the text. How can I go about it?

Answer 1

df
###
  Text HD/TTL
0  ABC     HD
1  DEF    NaN
2  GHI     HD
3  JKL    NaN
4  MNO    NaN
5  PQR     HD

g = df['HD/TTL'].notnull().cumsum()
v = df.groupby(g).apply(lambda x: x['Text'].str.cat(sep='\\n'))
output = pd.DataFrame({'HD': df.groupby(g)['HD/TTL'].first().values, 'Text': v}).reset_index(drop=True)
output
###
   HD           Text
0  HD       ABC\nDEF
1  HD  GHI\nJKL\nMNO
2  HD            PQR