Mastering CSV File Handling in Python

Table of Contents

Introduction
Reading a CSV File
Writing to a CSV File
Using DictReader and DictWriter
Handling Delimiters
Conclusion
Related Links

Introduction

CSV (Comma-Separated Values) is one of the most common file formats for handling tabular data. Python’s built-in csv module makes reading, writing, and editing CSV files straightforward and efficient.

Reading a CSV File

Use csv.reader to read a CSV file line by line:

import csv

with open('data.csv', newline='') as file:
    reader = csv.reader(file)
    for row in reader:
        print(row)

Writing to a CSV File

You can write rows to a CSV file using csv.writer:

import csv

data = [['Name', 'Score'], ['Alice', 90], ['Bob', 85]]

with open('output.csv', 'w', newline='') as file:
    writer = csv.writer(file)
    writer.writerows(data)

Using DictReader and DictWriter

If your CSV files have headers, DictReader and DictWriter are great tools.

import csv

# Reading with DictReader
with open('data.csv', newline='') as file:
    reader = csv.DictReader(file)
    for row in reader:
        print(row['Name'], row['Score'])

# Writing with DictWriter
with open('output.csv', 'w', newline='') as file:
    fieldnames = ['Name', 'Score']
    writer = csv.DictWriter(file, fieldnames=fieldnames)
    writer.writeheader()
    writer.writerow({'Name': 'Alice', 'Score': 90})

Handling Delimiters

You can change the delimiter if your CSV uses something other than a comma:

csv.reader(file, delimiter=';')

Conclusion

The csv module is a powerful way to handle structured data in Python. From simple tables to complex configurations, understanding CSV handling is essential for data-driven development.