Read Only First Column of pandas DataFrame in CSV File in Python (Example)


In this Python tutorial you’ll learn how to import only the first column of a CSV file.

Table of contents:

Here’s the step-by-step process:


Example Data & Add-On Libraries

We first have to import the pandas library, in order to use the functions that are contained in the library:

import pandas as pd                       # Import pandas library

We’ll also have to create some data that we can use in the exemplifying syntax below:

data = pd.DataFrame({'x1':range(1, 9),    # Create pandas DataFrame
                     'x2':[7, 3, 1, 5, 3, 3, 9, 8],
                     'x3':[5, 2, 5, 1, 4, 1, 4, 7],
                     'x4':['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h']})
print(data)                               # Print pandas DataFrame


table 1 DataFrame read only first column pandas dataframe csv file python


Have a look at the previous table. It shows that our example data consists of eight rows and four columns.

Let’s export these data to a CSV file:

data.to_csv('data.csv')                   # Export pandas DataFrame

At this point, you should find a new CSV file in your current working directory on your computer. We’ll use this CSV file for the example below.

Let’s continue!


Example: Read Only First Column from CSV File

The following syntax shows how to create a new pandas DataFrame from a CSV file that contains only the very first column of this file.

To achieve this, we have to set the usecols argument within the read_csv function to be equal to [1].

Consider the Python code below:

data_import = pd.read_csv('data.csv',     # Read first pandas DataFrame column
                           usecols = [1])
print(data_import)                        # Print imported pandas DataFrame


table 2 DataFrame read only first column pandas dataframe csv file python


In Table 2 you can see that we have created a new pandas DataFrame containing only the first column of our CSV file with the previous code.


Video & Further Resources

In case you need more information on the Python codes of this post, you might want to have a look at the following video on my YouTube channel. In the video, I illustrate the Python programming code of this tutorial in Python.


The YouTube video will be added soon.


Furthermore, you could have a look at some of the related posts on my homepage. A selection of articles is listed here.


Summary: In this tutorial you have learned how to read only the first column of a CSV file as a new pandas DataFrame in Python. Don’t hesitate to let me know in the comments section, in case you have additional comments or questions.


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