Convert Pandas Column to Lowercase

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  • Post category:Pandas
  • Post last modified:May 17, 2024
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You are currently viewing Convert Pandas Column to Lowercase

To convert a Pandas DataFrame column to lowercase, you can utilize methods like str.lower(), map(), apply(), or a 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.

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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

Below are quick examples of converting 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.


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 lowercase column

Pandas Convert Column to Lowercase using str.lower()

Pandas DataFrame column values can be converted to lowercase using the str.lower() function. This is a function from Series hence you can easily apply this function to a specific column. This syntax converts 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.

pandas lowercase column

Convert Pandas Column to Lowercase using apply()

Similarly, we can use the apply() function to convert a column in a Pandas DataFrame to lowercase. For instance, We use the apply() function to apply the str.lower() function to each element in the ‘Courses’ column of the DataFrame df. The str.lower() function is a built-in Python function that converts strings to lowercase.


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

# Output:
# Convert Pandas column to lower case:
#     Courses    Fee Duration  Discount
# 0    spark  22000   30days      1000
# 1  pyspark  25000   50days      2300
# 2   hadoop  24000   40days      2500
# 3   pandas  26000   60days      1400

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)

# Output:
# Convert Pandas column to lower case:
#     Courses    Fee Duration  Discount
# 0    spark  22000   30days      1000
# 1  pyspark  25000   50days      2300
# 2   hadoop  24000   40days      2500
# 3   pandas  26000   60days      1400

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)

# Output:
# Convert Pandas column to lower case:
#     Courses    Fee Duration  Discount
# 0    spark  22000   30days      1000
# 1  pyspark  25000   50days      2300
# 2   hadoop  24000   40days      2500
# 3   pandas  26000   60days      1400

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 !!

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