Convert Pandas Column to Lowercase

To convert a Pandas DataFrame column to lowercase, you can use the str.lower(), map(), apply(), and lambda function. This method allows you to apply a string function directly to each element of the column.

In this article, I will explain how to convert the entire contents of a column from uppercase to lowercase in a Pandas DataFrame with examples.

Key Points –

• Pandas provides the str.lower() method to convert string values to lowercase within a DataFrame column.
• Apply the str.lower() method to the desired column directly, or via the apply() function.
• Ensure the column data type is compatible with string operations before applying str.lower().
• The str.lower() method works efficiently with both string and object data types in Pandas DataFrame columns.

Quick Examples of Convert Lowercase Column Values

If you are in a hurry, below are some quick examples of how to convert lowercase column values in DataFrame.

# Quick examples of convert lowercase column values

# Example 1: convert lowercase column 
# Using str.lower()
df['Courses'] = df['Courses'].str.lower()

# Example 2: convert lowercase column 
# Using apply()
df['Courses'] = df['Courses'].apply(str.lower)

# Example 3: Use apply() & lambda function
df['Courses'].apply(lambda x: x.lower())

# Example 4: Convert pandas column 
# To lowercase use map()
df['Courses'] = df['Courses'].map(str.lower)

To run some examples of converting pandas column to lowercase, let’s create Pandas DataFrame using data from a dictionary.

import pandas as pd
import numpy as np
technologies= ({
    'Courses':["SPARK","PYSPARK","HADOOP","PANDAS"],
    'Fee' :[22000,25000,24000,26000],
    'Duration':['30days','50days','40days','60days'],
    'Discount':[1000,2300,2500,1400]
              })
df = pd.DataFrame(technologies)
print("Create DataFrame:\n", df)

Yields below output.

Pandas Convert Column to Lowercase using str.lower()

We can use str.lower() function to convert Pandas DataFrame column values to lowercase. This is a function from Series hence you can easily apply this function to a specific column. This syntax will convert specified column values from uppercase to lowercase. Here we convert the column values and assign it back to the same column.

# convert lowercase column use str.lower()
df['Courses'] = df['Courses'].str.lower()
print("Convert Pandas column to lower case:\n", df)

Yields below output.

Convert Pandas Column to Lowercase using apply()

Similarly, we can use apply() function to convert column values of a given DataFrame to lowercase. For that, we need to pass str.lower() function into apply() function and then, call the specified column of the given DataFrame. df['Courses']=df['Courses'].apply(str.lower) this syntax converts uppercase column values to lowercase column values.

# convert lowercase column use apply()
df['Courses'] = df['Courses'].apply(str.lower)
print("Convert Pandas column to lower case:\n", df)

Yields the same output as above.

Use apply() & Lambda Function

Alternatively, we can pass the lambda function into apply() function we can convert specified column values of a given DataFrame from uppercase to lowercase. Here, the lambda expression is used to construct an anonymous function.

# Use apply() & lambda function
df['Courses'].apply(lambda x: x.lower())
print("Convert Pandas column to lower case:\n", df)

Yields the same output as above.

Use map() Function

we can use the map() function to convert column values of a given DataFrame from uppercase to lowercase. For that, we need to pass str.lower() function into the map() function and then, call the specified column of the given DataFrame. df['Courses']=df['Courses'].map(str.lower) this syntax converts uppercase column values to lowercase column values.

# Convert pandas column to lowercase use map()
df['Courses'] = df['Courses'].map(str.lower)
print("Convert Pandas column to lower case:\n", df)

Yields the same output as above.

Complete Example For Lowercase Column Values

import pandas as pd
import numpy as np
technologies= ({
    'Courses':["SPARK","PYSPARK","HADOOP","PANDAS"],
    'Fee' :['22000','25000','24000','26000'],
    'Duration':['30days','50days','40days','60days'],
    'Discount':['1000','2300','2500','1400']
              })
df = pd.DataFrame(technologies)
print(df)

# convert lowercase column use str.lower()
df['Courses'] = df['Courses'].str.lower()
print(df)

# convert lowercase column use apply()
df['Courses'] = df['Courses'].apply(str.lower)
print(df)

# Use apply() & lambda function
df['Courses'].apply(lambda x: x.lower())
print(df)

# Convert pandas column to lowercase use map()
df['Courses'] = df['Courses'].map(str.lower)
print(df)

Conclusion

In this article, I have explained how to convert specified column values of a given DataFrame from uppercase to lowercase by using str.lower(), map(), apply(), and lambda function with examples.

Happy Learning !!

Related Articles

• Convert Pandas Index to List
• Pandas Convert String to Integer
• How to Use NOT IN Filter in Pandas
• Pandas DataFrame reindex() Function
• How to Convert List to Pandas Series
• Pandas Series.replace() – Replace Values
• Convert NumPy Array to Pandas DataFrame
• Convert Pandas Series of Lists to One Series
• Pandas – Convert DataFrame to JSON String
• Pandas – Convert DataFrame to Dictionary (Dict)

References

• https://pandas.pydata.org/pandas-docs/stable/reference/frame.html