Make new column in Panda dataframe by adding values from other columns

Question

I have a dataframe with values like

A B
1 4
2 6
3 9

I need to add a new column by adding values from column A and B, like

Answer 1

You could do:

df['C'] = df.sum(axis=1)

If you only want to do numerical values:

df['C'] = df.sum(axis=1, numeric_only=True)