Pandas: sum DataFrame rows for given columns

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I have the following DataFrame:

In [1]:
df = pd.DataFrame({'a': [1, 2, 3],
                   'b': [2, 3, 4],
                   'c': ['dd', 'ee', 'ff'],
                   'd': [5, 9, 1]})

df
Out [1]:
   a  b   c  d
0  1  2  dd  5
1  2  3  ee  9
2  3  4  ff  1

I would like to add a column 'e' which is the sum of columns 'a', 'b' and 'd'.

Going across forums, I thought something like this would work:

df['e'] = df[['a', 'b', 'd']].map(sum)

But it didn’t.

I would like to know the appropriate operation with the list of columns ['a', 'b', 'd'] and df as inputs.

8 Answers
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