Convert pandas DataFrame Index to List & NumPy Array in Python (2 Examples)

 

This article illustrates how to get the indices of a pandas DataFrame as a list or a NumPy array in the Python programming language.

The article will consist of two examples for the extraction of the indices of a pandas DataFrame as a list or a NumPy array. To be more specific, the content looks as follows:

Let’s jump right to the programming part.

 

Example Data & Libraries

In order to use the functions of the pandas library, we first need to load pandas:

import pandas as pd                        # Import pandas library

The following data is used as a basis for this Python programming tutorial:

data = pd.DataFrame({"x1":range(1, 10),    # Create pandas DataFrame
                     "x2":["a", "b", "c", "d", "e", "d", "c", "b", "a"],
                     "x3":range(10, 1, - 1)})
print(data)                                # Print pandas DataFrame

 

table 1 DataFrame convert pandas dataframe index list numpy array python

 

Table 1 shows the structure of the example DataFrame: It consists of nine rows and three columns and the index names are ranging from 0 to 8.

 

Example 1: Convert pandas DataFrame Index to List

Example 1 demonstrates how to extract the index names of a pandas DataFrame as a list object in Python.

To achieve this, we can use the index attribute and the tolist function as shown in the following Python syntax:

data_index1 = data.index.tolist()          # Extract as list object
print(data_index1)                         # Print index as list
# [0, 1, 2, 3, 4, 5, 6, 7, 8]

Have a look at the output of the previous Python code: We have created a new list object containing the index values of our input DataFrame.

 

Example 2: Convert pandas DataFrame Index to NumPy Array

Example 2 explains how to transform the index values of a pandas DataFrame to a NumPy array.

To return the indices as a NumPy array, we have to use the index.values attribute as shown below:

data_index2 = data.index.values            # Extract as NumPy array
print(data_index2)                         # Print index as NumPy array
# [0 1 2 3 4 5 6 7 8]

The previous output shows that we have created a new NumPy array containing the index range of our data set.

 

Video & Further Resources

I have recently published a video on my YouTube channel, which demonstrates the Python code of the present article. You can find the video below.

 

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In addition, you could read the related Python articles on my website. Some tutorials are listed below.

 

Summary: At this point in the article you should have learned how to extract the index names of a pandas DataFrame as a list or a NumPy array in the Python programming language. Tell me about it in the comments, if you have further questions.

 

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