Sum of every two columns and leave one column in pandas dataframe

Question

My task is like this:

df=pd.DataFrame([(1,2,3,4,5,6),(1,2,3,4,5,6),(1,2,3,4,5,6)],columns=['a','b','c','d','e','f'])
Out:
    a b c d e f
0   1 2 3 4 5 6
1   1 2 3 4 5 6 
2   1 2 3 4 5 6

I want to do is the output dataframe looks like this:

Out
        s1 b s2  d  s3  f
    0   3  2  7  4  11  6
    1   3  2  7  4  11  6
    2   3  2  7  4  11  6

That is to say, sum the column (a,b),(c,d),(e,f) separately and keep each last column and rename the result columns names as (s1,s2,s3). Could anyone help solve this problem in Pandas? Thank you so much.

Answer 1

You can seelct columns by posistions by iloc, sum each 2 values and last rename columns by f-strings

i = 2
for x in range(0, len(df.columns), i):
    df.iloc[:, x] = df.iloc[:, x:x+i].sum(axis=1)
    df = df.rename(columns={df.columns[x]:f's{x // i + 1}'})
print (df)
   s1  b  s2  d  s3  f
0   3  2   7  4  11  6
1   3  2   7  4  11  6
2   3  2   7  4  11  6