Python Pandas replace NaN in one column with value from corresponding row of second column

Assuming your DataFrame is in df:

df.Temp_Rating.fillna(df.Farheit, inplace=True)
del df['Farheit']
df.columns="File heat Observations".split()

First replace any NaN values with the corresponding value of df.Farheit. Delete the 'Farheit' column. Then rename the columns. Here’s the resulting DataFrame: