Pandas Lambda Function with Nan Support

Question

I am trying to write a lambda function in Pandas that checks to see if Col1 is a Nan and if so, uses another column\'s data. I have having trouble getting code (below) to c

Answer 1

Assuming that you do have a second column, that is:

df = pd.DataFrame({ 'Col1' : [1,2,3,np.NaN], 'Col2': [1,2,3,4]})

The correct solution to this problem would be:

df['Col1'].fillna(df['Col2'], inplace=True)