Merging and subtracting DataFrame columns in pandas?

Question

I have a pandas DataFrame, something like:

col1  col2 col3 col5
NaN    1    2    8
2     NaN   4    8
4     NaN   4    8

I want to do two t

Answer 1

In [58]:

df['newcol'] = df[['col1','col2']].sum(axis=1) - df['col5']
df['col3'] = df['col3'] - df['col5']
df
Out[58]:
   col1  col2  col3  col5  newcol
0   NaN     1    -6     8      -7
1     2   NaN    -4     8      -6
2     4   NaN    -4     8      -4

You can then drop col1 and col2:

In [59]:

df = df.drop(['col1','col2'],axis=1)
df
Out[59]:
   col3  col5  newcol
0    -6     8      -7
1    -4     8      -6
2    -4     8      -4