replace value in column with value from the column that has the value

Question

I'd like to replace the values in valcol with the values in the column which is the value. Suppose you have df looking something like below:

  col1 col2 col3 valcol
0    a    d    g   col1
1    b    e    h   col1
2    c    f    i   col2

I'd like the valcol_new to become this:

  col1 col2 col3 valcol valcol_new
0    a    d    g   col1          a
1    b    e    h   col1          b
2    c    f    i   col2          f

How would one do this?

df for testing:

df = pd.DataFrame({'col1': ['a', 'b', 'c'], 'col2': ['d', 'e', 'f'], 'col3': ['g', 'h', 'i'], 'valcol': ['col1', 'col1', 'col2']})

Answer 1

You can do this by enumerate() method and list comprehension and loc[] accessor:

df['valcol']=[df.loc[x,y] for x,y in enumerate(df['valcol'])]

Now if you print df you will get your desired output:

    col1    col2    col3    valcol
0   a       d       g       a
1   b       e       h       b
2   c       f       i       f