File Handling in Python

File handling is a fundamental skill for any programmer, allowing your applications to read from and write to the file system. This enables you to work with persistent data—information that is saved even after your program finishes running. From simple configuration files and logs to complex datasets and user-generated content, mastering file I/O (Input/Output) is essential for building real-world applications.

Python provides a powerful and intuitive built-in toolset for creating, reading, and manipulating files in various formats.

What You’ll Learn in This Guide

This section provides a comprehensive walkthrough of file handling in Python, from the basics of opening a file to working with structured data formats like CSV and JSON.

Introduction to File I/O

Understand the core concepts of file handling, why it’s essential, and the different types of files you can work with.

Basic File Operations

Learn the fundamental workflow: how to open files using different modes (r, w, a), read and write data, and properly close files using context managers.

Controlling the File Pointer

Master the seek() and tell() methods to read from or write to specific locations within a file, giving you precise control over the file cursor.

Robust Exception Handling

Write resilient code that can gracefully handle common file-related errors like FileNotFoundError and PermissionError.

Processing CSV Files

Use Python’s built-in csv module to easily read from and write to Comma-Separated Values (CSV) files, a common format for tabular data.

The with open(...) as f: syntax is the preferred way to work with files in Python. It automatically handles closing the file for you, even if errors occur. You will see this pattern used throughout the guide.

Practice Problems Introduction to File Handling