Splitting a string in a Python DataFrame

Question

I have a DataFrame in Python with a column with names (such as Joseph Haydn, Wolfgang Amadeus Mozart, Antonio Salieri and so forth).

I want to get a new column with the last names: Haydn, Mozart, Salieri and so forth.

I know how to split a string, but I could not find a way to apply it to a series, or a Data Frame column.

Answer 1

if you have:

import pandas
data = pandas.DataFrame({"composers": [ 
    "Joseph Haydn", 
    "Wolfgang Amadeus Mozart", 
    "Antonio Salieri",
    "Eumir Deodato"]})

assuming you want only the first name (and not the middle name like Amadeus):

data.composers.str.split('\s+').str[0]

will give:

0      Joseph
1    Wolfgang
2     Antonio
3       Eumir
dtype: object

you can assign this to a new column in the same dataframe:

data['firstnames'] = data.composers.str.split('\s+').str[0]

Last names would be:

data.composers.str.split('\s+').str[-1]

which gives:

0      Haydn
1     Mozart
2    Salieri
3    Deodato
dtype: object

(see also Python Pandas: selecting element in array column for accessing elements in an 'array' column)

For all but the last names you can apply " ".join(..) to all but the last element ( [:-1] ) of each row:

data.composers.str.split('\s+').str[:-1].apply(lambda parts: " ".join(parts))

which gives:

0              Joseph
1    Wolfgang Amadeus
2             Antonio
3               Eumir
dtype: object

Answer 2

Try this to solve your problem:

import pandas as pd
df = pd.DataFrame(
    {'composers':
        [ 
            'Joseph Haydn', 
            'Wolfgang Amadeus Mozart', 
            'Antonio Salieri',
            'Eumir Deodato',
        ]
    }
)

df['lastname'] = df['composers'].str.split(n = 0, expand = False).str[1]

You can now find the DataFrame, as shown below.

composers   lastname
0   Joseph Haydn    Haydn
1   Wolfgang Amadeus Mozart Amadeus Mozart
2   Antonio Salieri Salieri
3   Eumir Deodato   Deodato