Python CSV: Read and Write CSV Files

The CSV (Comma Separated Values) format is a common and straightforward way to store tabular data. To represent a CSV file, it should have the .csv file extension.

Now, let's proceed with an example of the info .csv file and its data.

SN, Name,    City
1,  Michael, New Jersey
2,  Jack,    California

Working With CSV Files in Python

Python provides a dedicated csv module to work with csv files. The module includes various methods to perform different operations.

However, we first need to import the module using:

import csv

Read CSV Files with Python

The csv module provides the csv.reader() function to read a CSV file.

Suppose we have a csv file named people.csv with the following entries.

Name,   Age, Profession
Jack,   23,  Doctor
Miller, 22,  Engineer

Now, let's read this csv file.

import csv

with open('people.csv', 'r') as file:
    reader = csv.reader(file)

    for row in reader:
        print(row)

Output

['Name', 'Age', 'Profession']
['Jack', '23', 'Doctor']
['Miller', '22', 'Engineer']

Here, we have opened the people.csv file in reading mode using:

with open(airtravel.csv', 'r') as file:

We then used the csv.reader() function to read the file. To learn more about reading csv files, Python Reading CSV Files.

Name,   Age, Profession
Jack,   23,  Doctor
Miller, 22,  Engineer

import csv
with open('people.csv', 'r') as file:
    csv_file = csv.DictReader(file)
    for row in csv_file:
        print(row)

{'SN': '1', ' Name': ' Michael', ' City': ' New Jersey'}
{'SN': '2', ' Name': ' Jack', ' City': ' California'}

Write to CSV Files with Python

The csv module provides the csv.writer() function to write to a CSV file.

Let's look at an example.

import csv
with open('protagonist.csv', 'w', newline='') as file:
    writer = csv.writer(file)
    writer.writerow(["SN", "Movie", "Protagonist"])
    writer.writerow([1, "Lord of the Rings", "Frodo Baggins"])
    writer.writerow([2, "Harry Potter", "Harry Potter"])

When we run the above program, a protagonist.csv file is created with the following content:

SN,Movie,Protagonist
1,Lord of the Rings,Frodo Baggins
2,Harry Potter,Harry Potter

In this example, we have created the CSV file named protagonist.csv in the writing mode.

We then used the csv.writer() function to write to the file. To learn more about writing to a csv file, Python Writing CSV Files.

Here,

• writer.writerow(["SN", "Movie", "Protagonist"]) writes the header row with column names to the CSV file.
• writer.writerow([1, "Lord of the Rings", "Frodo Baggins"]) writes the first data row to the CSV file.
• writer.writerow([2, "Harry Potter", "Harry Potter"]) writes the second data row to the CSV file.

import csv

with open('players.csv', 'w', newline='') as file:
    fieldnames = ['player_name', 'fide_rating']
    writer = csv.DictWriter(file, fieldnames=fieldnames)

    writer.writeheader()
    writer.writerow({'player_name': 'Magnus Carlsen', 'fide_rating': 2870})
    writer.writerow({'player_name': 'Fabiano Caruana', 'fide_rating': 2822})
    writer.writerow({'player_name': 'Ding Liren', 'fide_rating': 2801})

player_name,fide_rating
Magnus Carlsen,2870
Fabiano Caruana,2822
Ding Liren,2801

Using Python Pandas to Handle CSV Files

Pandas is a popular data science library in Python for data manipulation and analysis.

If we are working with huge chunks of data, it's better to use pandas to handle CSV files for ease and efficiency.

Note: Before we can use pandas, we need to install and import it. To learn more, visit Install and Import Pandas.

Read CSV Files

To read the CSV file using pandas, we can use the read_csv() function.

import pandas as pd
pd.read_csv("people.csv")

Here, the program reads people.csv from the current directory.

Write to a CSV Files

To write to a CSV file, we need to use the to_csv() function of a DataFrame.

import pandas as pd

# creating a data frame
df = pd.DataFrame([['Jack', 24], ['Rose', 22]], columns = ['Name', 'Age'])

# writing data frame to a CSV file
df.to_csv('person.csv')

Here, we have created a DataFrame using the pd.DataFrame() method. Then, the to_csv() function for this object is called, to write into person.csv.

Also Read

• Python File Operation