pandas: combine two columns in a DataFrame

Question

I have a pandas DataFrame that has multiple columns in it:

Index: 239897 entries, 2012-05-11 15:20:00 to 2012-06-02 23:44:51
Data columns:
foo           


        

Answer 1

You can do this using numpy too.

df['bar'] = np.where(pd.isnull(df['bar']),df['foo'],df['bar'])