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

Another option, use the .apply() method on the frame. You can do reassign a column with deference to existing data...

import pandas as pd
import numpy as np

# get your data into a dataframe

# replace content in "bar" with "foo" if "bar" is null
df["bar"] = df.apply(lambda row: row["foo"] if row["bar"] == np.NaN else row["bar"], axis=1) 

# note: change 'np.NaN' with null values you have like an empty string