Python Pandas add column for row-wise max value of selected columns

Question

data = {'name' : ['bill', 'joe', 'steve'],

    'test1' : [85, 75, 85],

    'test2' : [35, 45, 83],

     'test3' : [51, 61, 45]}

frame = pd.DataFrame(data)

I would like to add a new column that shows the max value for each row.

desired output:

 name test1 test2 test3 HighScore

 bill  75    75    85    85

 joe   35    45    83    83 

 steve  51   61    45    61 

Sometimes

frame['HighScore'] = max(data['test1'], data['test2'], data['test3'])

works but most of the time gives this error:

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

Why does it only work sometimes? Is there another way of doing it?

Answer 1

Use this code:

>>> frame['HighScore'] = frame[['test1','test2','test3']].max(axis=1)

>>> frame

    name  test1  test2  test3  HighScore

0   bill     85     35     51         85

1    joe     75     45     61         75

2  steve     85     83     45         85

Here, max(axis=1) is for getting the row-wise max and  max(axis=0) is for column-wise max.

You can refer to our Python online course for more information.