CODEWITHSUNDEEP
pythonstringpandasdataframeconcatenation
Zubo
Zubo

Reputation: 1593

Concatenate string columns and index

I have a DataFrame like this: 

A    B
----------
c    d
e    f

I'd like to introduce a third column, made up of a concatenation of A, B and the index, so that the DataFrame becomes: 

A    B    C
---------------
c    d    cd0
e    f    ef1

I'd like to do that like so: 

df['C'] = df['A'] + df['B'] + # and here I don't know how to reference the row index.

How can I do this?

Upvotes: 2

Views: 3514

Answers (3)

piRSquared
piRSquared

Reputation: 294278

With pd.DataFrame.itertuples
Python 3.6

df.assign(C=[f'{a}{b}{i}' for i, a, b in df.itertuples()])

   A  B    C
0  c  d  cd0
1  e  f  ef1

With pd.Series.str.cat 

df.assign(C=df.A.str.cat(df.B).str.cat(df.index.astype(str)))

   A  B    C
0  c  d  cd0
1  e  f  ef1

Mish/Mash 

from operator import add
from functools import reduce
from itertools import chain

df.assign(C=reduce(add, chain((df[c] for c in df), [df.index.astype(str)])))

   A  B    C
0  c  d  cd0
1  e  f  ef1

Summation 

df.assign(C=df.sum(1) + df.index.astype(str))

   A  B    C
0  c  d  cd0
1  e  f  ef1

Upvotes: 4

n3utrino
n3utrino

Reputation: 1210

df['C'] = df['A'].astype(str) + df['B'].astype(str) + np.array(map(str, df.index.values))

Basically you access the df index with df.index, and to turn that into a numpy array you add the .values, and to convert that into a string (to easily add to the previous columns, which are strings), you can use a map function.

Edit: added .astype(str) to columns A and B, to convert them to strings. If they are already strings, this won't be necessary.

Upvotes: 0

cs95
cs95

Reputation: 402523

Option 1
For better scalability, use assign + agg:

df['C'] = df.assign(index=df.index.astype(str)).agg(''.join, 1)
df

   A  B    C
0  c  d  cd0
1  e  f  ef1

Or, using np.add.reduce in a similar fashion:

df['C'] = np.add.reduce(df.assign(index=df.index.astype(str)), axis=1)
df

   A  B    C
0  c  d  cd0
1  e  f  ef1

Option 2
A less scalable option using vectorised string concatenation:

df['C'] = df['A'] + df['B'] + df.index.astype(str)
df

   A  B    C
0  c  d  cd0
1  e  f  ef1

Upvotes: 7

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