In [1]: import pandas as pd
Data used for this tutorial:
  • This tutorial uses the Titanic data set, stored as CSV. The data consists of the following data columns:

    • PassengerId: Id of every passenger.

    • Survived: This feature have value 0 and 1. 0 for not survived and 1 for survived.

    • Pclass: There are 3 classes: Class 1, Class 2 and Class 3.

    • Name: Name of passenger.

    • Sex: Gender of passenger.

    • Age: Age of passenger.

    • SibSp: Indication that passenger have siblings and spouse.

    • Parch: Whether a passenger is alone or have family.

    • Ticket: Ticket number of passenger.

    • Fare: Indicating the fare.

    • Cabin: The cabin of passenger.

    • Embarked: The embarked category.

    To raw data
    In [2]: titanic = pd.read_csv("data/titanic.csv")
    In [3]: titanic.head()
       PassengerId  Survived  Pclass                                               Name     Sex  ...  Parch            Ticket     Fare Cabin  Embarked
    0            1         0       3                            Braund, Mr. Owen Harris    male  ...      0         A/5 21171   7.2500   NaN         S
    1            2         1       1  Cumings, Mrs. John Bradley (Florence Briggs Th...  female  ...      0          PC 17599  71.2833   C85         C
    2            3         1       3                             Heikkinen, Miss. Laina  female  ...      0  STON/O2. 3101282   7.9250   NaN         S
    3            4         1       1       Futrelle, Mrs. Jacques Heath (Lily May Peel)  female  ...      0            113803  53.1000  C123         S
    4            5         0       3                           Allen, Mr. William Henry    male  ...      0            373450   8.0500   NaN         S
    [5 rows x 12 columns]

How to manipulate textual data?

  • Make all name characters lowercase

    In [4]: titanic["Name"].str.lower()
    0                                braund, mr. owen harris
    1      cumings, mrs. john bradley (florence briggs th...
    2                                 heikkinen, miss. laina
    3           futrelle, mrs. jacques heath (lily may peel)
    4                               allen, mr. william henry
    886                                montvila, rev. juozas
    887                         graham, miss. margaret edith
    888             johnston, miss. catherine helen "carrie"
    889                                behr, mr. karl howell
    890                                  dooley, mr. patrick
    Name: Name, Length: 891, dtype: object

    To make each of the strings in the Name column lowercase, select the Name column (see tutorial on selection of data), add the str accessor and apply the lower method. As such, each of the strings is converted element wise.

Similar to datetime objects in the time series tutorial having a dt accessor, a number of specialized string methods are available when using the str accessor. These methods have in general matching names with the equivalent built-in string methods for single elements, but are applied element-wise (remember element wise calculations?) on each of the values of the columns.

  • Create a new column Surname that contains the surname of the Passengers by extracting the part before the comma.

    In [5]: titanic["Name"].str.split(",")
    0                             [Braund,  Mr. Owen Harris]
    1      [Cumings,  Mrs. John Bradley (Florence Briggs ...
    2                              [Heikkinen,  Miss. Laina]
    3        [Futrelle,  Mrs. Jacques Heath (Lily May Peel)]
    4                            [Allen,  Mr. William Henry]
    886                             [Montvila,  Rev. Juozas]
    887                      [Graham,  Miss. Margaret Edith]
    888          [Johnston,  Miss. Catherine Helen "Carrie"]
    889                             [Behr,  Mr. Karl Howell]
    890                               [Dooley,  Mr. Patrick]
    Name: Name, Length: 891, dtype: object

    Using the Series.str.split() method, each of the values is returned as a list of 2 elements. The first element is the part before the comma and the second element is the part after the comma.

    In [6]: titanic["Surname"] = titanic["Name"].str.split(",").str.get(0)
    In [7]: titanic["Surname"]
    0         Braund
    1        Cumings
    2      Heikkinen
    3       Futrelle
    4          Allen
    886     Montvila
    887       Graham
    888     Johnston
    889         Behr
    890       Dooley
    Name: Surname, Length: 891, dtype: object

    As we are only interested in the first part representing the surname (element 0), we can again use the str accessor and apply Series.str.get() to extract the relevant part. Indeed, these string functions can be concatenated to combine multiple functions at once!

To user guide

More information on extracting parts of strings is available in the user guide section on splitting and replacing strings.

  • Extract the passenger data about the Countesses on board of the Titanic.

    In [8]: titanic["Name"].str.contains("Countess")
    0      False
    1      False
    2      False
    3      False
    4      False
    886    False
    887    False
    888    False
    889    False
    890    False
    Name: Name, Length: 891, dtype: bool
    In [9]: titanic[titanic["Name"].str.contains("Countess")]
         PassengerId  Survived  Pclass                                               Name     Sex  ...  Ticket  Fare  Cabin Embarked  Surname
    759          760         1       1  Rothes, the Countess. of (Lucy Noel Martha Dye...  female  ...  110152  86.5    B77        S   Rothes
    [1 rows x 13 columns]

    (Interested in her story? See *`Wikipedia <,_Countess_of_Rothes>`__*!)

    The string method Series.str.contains() checks for each of the values in the column Name if the string contains the word Countess and returns for each of the values True (Countess is part of the name) of False (Countess is not part of the name). This output can be used to subselect the data using conditional (boolean) indexing introduced in the subsetting of data tutorial. As there was only one Countess on the Titanic, we get one row as a result.


More powerful extractions on strings are supported, as the Series.str.contains() and Series.str.extract() methods accept regular expressions, but out of scope of this tutorial.

To user guide

More information on extracting parts of strings is available in the user guide section on string matching and extracting.

  • Which passenger of the Titanic has the longest name?

    In [10]: titanic["Name"].str.len()
    0      23
    1      51
    2      22
    3      44
    4      24
    886    21
    887    28
    888    40
    889    21
    890    19
    Name: Name, Length: 891, dtype: int64

    To get the longest name we first have to get the lengths of each of the names in the Name column. By using pandas string methods, the Series.str.len() function is applied to each of the names individually (element-wise).

    In [11]: titanic["Name"].str.len().idxmax()
    Out[11]: 307

    Next, we need to get the corresponding location, preferably the index label, in the table for which the name length is the largest. The idxmax() method does exactly that. It is not a string method and is applied to integers, so no str is used.

    In [12]: titanic.loc[titanic["Name"].str.len().idxmax(), "Name"]
    Out[12]: 'Penasco y Castellana, Mrs. Victor de Satode (Maria Josefa Perez de Soto y Vallejo)'

    Based on the index name of the row (307) and the column (Name), we can do a selection using the loc operator, introduced in the tutorial on subsetting.

  • In the “Sex” column, replace values of “male” by “M” and values of “female” by “F”

    In [13]: titanic["Sex_short"] = titanic["Sex"].replace({"male": "M",
       ....:                                                "female": "F"})
    In [14]: titanic["Sex_short"]
    0      M
    1      F
    2      F
    3      F
    4      M
    886    M
    887    F
    888    F
    889    M
    890    M
    Name: Sex_short, Length: 891, dtype: object

    Whereas replace() is not a string method, it provides a convenient way to use mappings or vocabularies to translate certain values. It requires a dictionary to define the mapping {from : to}.


There is also a replace() method available to replace a specific set of characters. However, when having a mapping of multiple values, this would become:

titanic["Sex_short"] = titanic["Sex"].str.replace("female", "F")
titanic["Sex_short"] = titanic["Sex_short"].str.replace("male", "M")

This would become cumbersome and easily lead to mistakes. Just think (or try out yourself) what would happen if those two statements are applied in the opposite order…


  • String methods are available using the str accessor.

  • String methods work element wise and can be used for conditional indexing.

  • The replace method is a convenient method to convert values according to a given dictionary.

To user guide

A full overview is provided in the user guide pages on working with text data.