Pandas sum DataFrame rows for given columns

Question

I have the following DataFrame   In  1    import pandas as pd 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 column  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

User · Answer

This is a simpler way using iloc to select which columns to sum:

df['f']=df.iloc[:,0:2].sum(axis=1)
df['g']=df.iloc[:,[0,1]].sum(axis=1)
df['h']=df.iloc[:,[0,3]].sum(axis=1)

Produces:

   a  b   c  d   e  f  g   h
0  1  2  dd  5   8  3  3   6
1  2  3  ee  9  14  5  5  11
2  3  4  ff  1   8  7  7   4

I can't find a way to combine a range and specific columns that works e.g. something like:

df['i']=df.iloc[:,[[0:2],3]].sum(axis=1)
df['i']=df.iloc[:,[0:2,3]].sum(axis=1)

User · Answer

You can simply pass your dataframe into the following function    def sum frame by column frame  new col name  list of cols to sum       frame new col name    frame list of cols to sum  astype float  sum axis 1      return frame    Example    I have a dataframe  awards frame  as follows         and I want to create a new column that shows the sum of awards for each row   Usage    I simply pass my awards frame into the function  also specifying the name of the new column  and a list of column names that are to be summed    sum frame by column awards frame   award sum     award 1   award 2   award 3      Result

User · Answer

Create a list of column names you want to add up   df  total   df loc   list name  sum axis 1    If you want the sum for certain rows  specify the rows using

User · Answer

You can just sum and set param axis 1 to sum the rows  this will ignore none numeric columns   In  91    df   pd DataFrame   a    1 2 3    b    2 3 4    c    dd   ee   ff     d   5 9 1    df  e     df sum axis 1  df Out 91      a  b   c  d   e 0  1  2  dd  5   8 1  2  3  ee  9  14 2  3  4  ff  1   8   If you want to just sum specific columns then you can create a list of the columns and remove the ones you are not interested in   In  98    col list  list df  col list remove  d   col list Out 98     a    b    c   In  99    df  e     df col list  sum axis 1  df Out 99      a  b   c  d  e 0  1  2  dd  5  3 1  2  3  ee  9  5 2  3  4  ff  1  7

User · Answer

If you have just a few columns to sum  you can write    df  e     df  a     df  b     df  d     This creates new column e with the values      a  b   c  d   e 0  1  2  dd  5   8 1  2  3  ee  9  14 2  3  4  ff  1   8   For longer lists of columns  EdChum s answer is preferred

User · Answer

The shortest and simpliest way here is to use      df eval  e   a   b   d

User · Answer

Following syntax helped me when I have columns in sequence   awards frame values   1 4  sum axis  1

[python] Pandas: sum DataFrame rows for given columns

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