append same string to list of strings in a column pandas

Question

I have a df:

    a   b       c
0  'd'  1  ['f', 'h']
1  'f'  2  ['u', 'v']
2  'g'  3  ['i', 'o']

I want to append df['a'] to each element of df['c'] column. expected output:

    a   b       c          d
0  'd'  1  ['f', 'h']  ['fd', 'hd']
1  'f'  2  ['u', 'v']  ['uf', 'vf']
2  'g'  3  ['i', 'o']  ['ig', 'og']

I tried for loops, and an attempt at list comprehension, but it was garbage. To avoid for loops, I have tried this vectorized approach. But did not work.

df['d']=df['c'].cat(df['a'],axis=0).values.tolist()

As always, any help, much appreciated.

That is not a correct representation of a list of strings. The strings should be enclosed in paranthesis, like ['f', 'h'] — Erfan
– Erfan, Commented Dec 19, 2020 at 14:00
yes. sorry for wrong representation. please find the update now. — anjali
– anjali, Commented Dec 19, 2020 at 14:03

Erfan · Accepted Answer · 2020-12-19 14:04:20Z

2

We can use explode to unnest your list, then add the strings together and finally use groupby on the index and use agg(list) to get your list back:

ex = df.explode('c')
ex['c'] = ex['c'] + ex['a']

df['c'] = ex.groupby(ex.index)['c'].agg(list)

   a  b         c
0  d  1  [fd, hd]
1  f  2  [uf, vf]
2  g  3  [ig, og]

answered Dec 19, 2020 at 14:04

Erfan

43.3k10 gold badges75 silver badges86 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

append same string to list of strings in a column pandas

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related