Creating multiple feature-columns using apply (or something else) on pandas column

Question

I have a dataframe:

df = pd.DataFrame({'col1': [69, 77, 88],
                   'col2': ['barfoo', 'foo', 'bar']})
print(df)

   col1    col2
0    69  barfoo
1    77     foo
2    88     bar

Also I have function that returns two values based on string:

def get_first_n_second(string):
    '''
    Function returns two values for two columns
    '''
    value1 = string[0]
    value2 = string[1]
    return value1, value2

And I want to create two new columns based on col2 (it doesn`t work):

df[['first', 'second']] = df['col2'].apply(get_first_n_second)

Desired output:

   col1    col2   first   second
0    69  barfoo       b        a
1    77     foo       f        o
2    88     bar       b        a

jezrael · Accepted Answer · 2020-08-18 08:07:55Z

2

There are 2 changes - return Series from function:

def get_first_n_second(string):
    '''
    Function returns two values for two columns
    '''
    value1 = string[0]
    value2 = string[1]
    return pd.Series([value1, value2])


df[['first', 'second']] = df['col2'].apply(get_first_n_second)
print (df)
   col1    col2 first second
0    69  barfoo     b      a
1    77     foo     f      o
2    88     bar     b      a

edited Aug 18, 2020 at 8:07

answered Aug 18, 2020 at 8:04

jezrael

868k103 gold badges1.4k silver badges1.3k bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Warrior404 Over a year ago

Yes, i mentiond mistake about apply on full dataframe. It was accidentally.

jezrael Over a year ago

@Warrior404 - No problem ;)

anon01 · Accepted Answer · 2020-08-18 08:20:08Z

2

Alternative: use the built in str methods. It may(?) be more efficient to use the built in functions than .apply:

df['first'] = df['col2'].str[0]
df['second'] = df['col2'].str[1]

answered Aug 18, 2020 at 8:20

anon01

11.2k8 gold badges41 silver badges64 bronze badges

1 Comment

Warrior404 Over a year ago

In this case, i think, your solution is better and easier, but there are more complex function in my real project. So str method dont have such methods. But thank you anyway.

Collectives™ on Stack Overflow

Creating multiple feature-columns using apply (or something else) on pandas column

2 Answers 2

2 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related