Pandas Series.str.casefold() Method

TheSeries.str.casefold() method in Pandas is used to convert strings in a Series or Index to be casefolded. Casefolding is a more aggressive form of lower casing used for text normalization. It is especially useful for performing case-insensitive comparisons and for handling text in a more uniform manner.

This method is equivalent to Python's built-instr.casefold() method and is typically used to standardize text data in data analysis tasks.

Syntax

Following is the syntax of the Pandas Series.str.casefold() method −

Series.str.casefold()

Parameters

The PandasSeries.str.casefold() method does not accept any parameters.

Return Value

TheSeries.str.casefold() method returns a Series or Index of the same shape, where each string has been casefolded. This means that all characters in each string are converted to their casefolded (lowercase) form.

Example 1

Let's look at a basic example to understand how theSeries.str.casefold() method works −

import pandas as pd# Create a Seriess = pd.Series(['Hi', 'WELCOME to', 'TUTORIALSPOINT'])# Display the input Seriesprint("Input Series")print(s)# Apply the casefold methodprint("Series after applying the casefold:")print(s.str.casefold())

When we run the above program, it produces the following result −

Input Series0                Hi1        WELCOME to2    TUTORIALSPOINTdtype: objectSeries after applying the casefold:0                hi1        welcome to2    tutorialspointdtype: object

Example 2

In this example, we'll demonstrate the use of theSeries.str.casefold() method in a DataFrame −

import pandas as pd# Create a DataFramedf = pd.DataFrame({'Day': ['Mon', 'Tue', 'Wed', 'Thu', 'Fri'], 'Subject': ['Math', 'English', 'Science', 'Music', 'Games']})# Print the original DataFrameprint("Input DataFrame")print(df)# Apply the casefold method to the 'Day' columndf.Day = df.Day.str.casefold()# Print the modified DataFrameprint("Modified DataFrame:")print(df)

Following is the output of the above code −

Original DataFrame:   Day  Subject0  Mon     Math1  Tue  English2  Wed  Science3  Thu    Music4  Fri    GamesModified DataFrame:   Day  Subject0  mon     Math1  tue  English2  wed  Science3  thu    Music4  fri    Games

Example 3

Let's see another example where we applySeries.str.casefold() in a more complex scenario −

import pandas as pd# Create a DataFrame with mixed-case textdf = pd.DataFrame({'Name': ['Alice', 'Bob', 'CHARLIE', 'david'], 'Role': ['Admin', 'user', 'MANAGER', 'staff']})# Print the original DataFrameprint("Original DataFrame:")print(df)# Apply casefold to both 'Name' and 'Role' columnsdf = df.apply(lambda x: x.str.casefold() if x.dtype == "object" else x)# Print the modified DataFrameprint("Modified DataFrame:")print(df)

Output of the above code is as follows −

Original DataFrame:      Name     Role0    Alice    Admin1      Bob     user2  CHARLIE  MANAGER3    david    staffModified DataFrame:      Name     Role0    alice    admin1      bob     user2  charlie  manager3    david    staff