How can I abstract a value from another column with a condition?

Question

I want to create a column, based on values in another column. I found this approach, but I don't think that this is going to work, since I need to check all the 'Unique_String' values, before 'abstracting' the data.

What do I want?

I want to 'loop'(?) through my 'Text' column, see if there is data available. If not, it should look into the 'Unique_String' column, and abstract (if available) the values, and paste it into the Text column.

Data

I have a dataframe like this:

Unique_String                 Text 
AAA                           Here is text! 
AAA                           nan
BBB                           nan
BBB                           Here is text as well! 
BBB                           Feyenoord
CCC                           nan
CCC                           nan

The desired output is:

Unique_String                 Text 
AAA                           Here is text! 
AAA                           Here is text!
BBB                           Here is text as well!
BBB                           Here is text as well! 
BBB                           Feyenoord
CCC                           nan
CCC                           nan 

Many Thanks!

Answer 1

Here is necessary call functions forward and back filling per groups:

df['Text'] = df.groupby('Unique_String')['Text'].apply(lambda x: x.ffill().bfill())
print (df)
  Unique_String                   Text
0           AAA          Here is text!
1           AAA          Here is text!
2           BBB  Here is text as well!
3           BBB  Here is text as well!
4           BBB              Feyenoord
5           CCC                    NaN
6           CCC                    NaN