Assigning value to a new column based on the values of other columns in Pandas

Question

The following is a sub-set of data frame:

id  words  A   B   C   D  E  
1   new    1       1   
2   good   1  
3   star            1
4   never                  
5   final   

I want to define a new variable (called FF) as a new column and assign 1 to it, if values for all other variables (columns) are "null". The new data frame would be like this:

id  words  A   B   C   D  E  FF
1   new    1       1   
2   good   1  
3   star            1
4   never                     1                
5   final                     1

How I can do it using python and Pandas ? Thanks.

Answer 1

You can define a function that is applied row-wise to the data frame:

def fill_if_nan(row):
    if row[['A', 'B', 'C', 'D', 'E']].isnull().all():
        return 1

    return None

df['FF'] = df.apply(fill_if_nan, axis=1)

Or a more elegant numpy based solution:

df['FF'] = np.where(df[['A', 'B', 'C', 'D', 'E']].isnull().all(1), 1, np.nan)