How to conditionally update DataFrame column in Pandas

Question

With this DataFrame, how can I conditionally set rating to 0 when line_race is equal to zero?

    line_track  line_race  rating fo         


        

Answer 1

Use numpy.where to say if ColumnA = x then ColumnB = y else ColumnB = ColumnB:

df['rating'] = np.where(df['line_race']==0, 0, df['rating'])