A Guide to Getting a List of Columns from a Pandas DataFrame

Pandas, a staple in the Python data analysis toolkit, offers a powerful data structure called the DataFrame . At its core, a DataFrame is a two-dimensional labeled data structure, akin to tables in SQL, Excel spreadsheets, or data frames in R. One of the most common tasks when working with DataFrames is extracting the column names. Let's delve into how you can obtain a list of columns from a Pandas DataFrame.

1. Creating a Simple DataFrame

link to this section

Before we begin, let's create a sample DataFrame for demonstration purposes: 

import pandas as pd 
    
data = { 
    'Name': ['Alice', 'Bob', 'Charlie', 'David'], 
    'Age': [25, 30, 35, 40], 
    'City': ['New York', 'San Francisco', 'Los Angeles', 'Chicago'] 
} 

df = pd.DataFrame(data)

This DataFrame df has three columns: Name , Age , and City .

2. Getting the List of Columns

link to this section

The simplest way to extract the columns is using the columns attribute of the DataFrame: 

columns_list = df.columns print(columns_list)

Output: 

Index(['Name', 'Age', 'City'], dtype='object')

Notice that the output is not a standard Python list but an Index object. While this Index object can often be used like a list in many contexts, if you specifically need a Python list, you can easily convert it: 

columns_list = df.columns.tolist() 
print(columns_list)

Output: 

['Name', 'Age', 'City']

3. Iterating Through Columns

link to this section

You can also iterate through the columns of a DataFrame, which can be useful in various scenarios, like renaming columns based on certain criteria: 

for col in df.columns: 
    print(col)

Output: 

Name Age City

4. Selecting Specific Columns

link to this section

Once you have the list of columns, you can use it to filter or select specific columns from the DataFrame: 

selected_columns = ['Name', 'City'] 
new_df = df[selected_columns] 
print(new_df)

5. Bonus Tip: Getting Columns with Specific Data Types

link to this section

Sometimes, you might want to get columns based on their data types. For instance, you may want to extract only numerical columns: 

numerical_columns = df.select_dtypes(include=['number']).columns.tolist() 
print(numerical_columns)

Output: 

['Age']

Conclusion

link to this section

Extracting column names is a fundamental operation when working with Pandas DataFrames. Whether you're trying to understand your dataset's structure, renaming columns, or selecting specific columns, being proficient in this task will undoubtedly benefit your data analysis processes. The Pandas library provides intuitive and efficient methods, such as the columns attribute, to make this process seamless.