File Handling in Python

Learn how Python can create, read, write, update and manage files stored on a computer.

What is File Handling?

File handling means working with files using a program.

In Python, we can use file handling to read existing data from a file, create new files, write data into files and update existing file content.

Simple Definition: File handling is the process of reading, writing, creating and managing files using Python.

Why Do We Need File Handling?

Variables store data temporarily while a program is running. Files allow us to store data so that it can be used again later.

Store Data

Save information permanently in files.

Read Data

Read previously stored information.

Process Data

Use file data inside Python programs.

File Handling Diagram

A basic file-handling process can be understood through these steps:

Python Program

Application needs to work with stored data.

↓

Open

Open the file using open().

Read

Get data from the file.

Write

Add or update file data.

Close

Finish using the file.

↓

Stored File

Data remains available for future use.

Opening a File

Python provides the built-in open() function to work with files.

file = open("example.txt", "r")

Here:

example.txt is the file name.
"r" means read mode.
file stores the file object.

File Opening Modes

The mode tells Python what we want to do with the file.

Mode	Meaning
`r`	Read the file.
`w`	Write to the file. Existing content can be replaced.
`a`	Add data to the end of the file.
`x`	Create a new file and fail if it already exists.
`rb`	Read a binary file.
`wb`	Write binary data.

Reading a File

The read() method is used to read the file content.

file = open("example.txt", "r")

data = file.read()

print(data)

file.close()

This reads the complete content of the file.

Writing to a File

The w mode is used to write data.

file = open("example.txt", "w")

file.write("Hello Python")

file.close()

The text is written into the file.

Important: Write mode can replace existing content in the file. Use it carefully when existing data must be preserved.

Appending Data

The a mode adds new data at the end of the file.

file = open("example.txt", "a")

file.write("\nWelcome to Python")

file.close()

Existing content is kept and the new content is added at the end.

Using the `with` Statement

Python provides the with statement to work with files more safely and conveniently.

with open("example.txt", "r") as file:

    data = file.read()

    print(data)

After the with block finishes, Python handles the file resource automatically.

Common File Methods

Method	Purpose
`read()`	Reads the file content.
`readline()`	Reads one line.
`readlines()`	Reads lines into a list.
`write()`	Writes text to a file.
`writelines()`	Writes multiple strings.
`close()`	Closes the file.

Text Files and Binary Files

Files are commonly handled in two broad forms: text and binary.

Text Files

Store text-based content such as:

TXT files
CSV files
JSON files

Binary Files

Store data such as:

Images
PDF files
Other binary content

Basic File Handling Flow

Step 1: Decide which file you need to work with.

↓

Step 2: Open the file using the required mode.

↓

Step 3: Read or write data.

↓

Step 4: Save or finish the operation.

↓

Step 5: Close or automatically release the file resource.

Example 👀🔓

Suppose a training institute wants to store student information.

Name,Course,Fees
Rahul,Python,45000
Priya,Java,40000

Python can read this information from a file, process it and save updated information.

Later in this module we will learn how to work with CSV and JSON files in more detail.

Common Mistakes

Using the wrong file path.
Using the wrong file mode.
Forgetting to close a file when not using the with statement.
Accidentally replacing existing content with write mode.
Trying to read a file that does not exist.

Practice Programs

Create a text file using Python.
Write three lines into the file.
Read the complete file content.
Read the file one line at a time.
Append new data to the file.
Read a file using the with statement.

File Handling Topics

Reading Files

Read text and data from files.

Writing Files

Create and write file content.

Files & Directories

Work with paths, files and folders.

CSV Files

Read and write CSV data.

JSON Files

Read and write JSON data.

Practice

Apply file-handling concepts in programs.

Summary

File handling allows Python programs to work with stored data. The open() function is used to open files in different modes such as r, w and a. Python provides methods such as read(), write() and close(). The with statement provides a convenient way to work with files and handle the file resource automatically. In the upcoming topics, we will study reading files, writing files, directories, CSV files and JSON files in detail.

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