File Handling in Python: A Complete Guide for Class 12 NCERT Students

Understanding File Types: Text vs Binary Files

Files in computers are sequences of bytes storing data in two main types:

• Text Files: These contain human-readable characters such as alphabets, digits, and symbols. Examples include .txt, .py, and .csv files. When opened in editors like Notepad, their content is readable.
• Binary Files: These store data in bytes not corresponding to readable characters, such as images, audio, videos, or executable files. Opening binary files in text editors shows unreadable characters.

Each character in a text file is stored using ASCII or Unicode values. For example, the letter 'A' is stored as ASCII value 65. Text files use special characters like newline \n to mark the end of lines.

Understanding these file types helps you choose the right mode and method when handling files in Python.

File Modes in Python: How to Open Files Correctly

Python provides various modes to open files depending on the operation:

Example:

To open a file named story.txt in write mode:

``python f = open(r"D:\TEMP\story.txt", "w") ``

Choosing the correct mode is essential to avoid data loss or errors.

Basic File Operations: Reading and Writing in Python

Once a file is opened, Python allows you to perform operations like reading and writing.

• Reading Files: Use read(), readline(), or readlines() methods.

``python f = open("file.txt", "r") content = f.read() # Reads entire file f.close() ``

• Writing Files: Use the write() method to add content.

``python f = open("file.txt", "w") f.write("Hello, Class 12 students!") f.close() ``

• Appending Files: Use append mode a to add data without deleting existing content.

``python f = open("file.txt", "a") f.write(" More data appended.") f.close() ``

Always close files after operations to free resources and save data properly.

Working with File Pointers and Positioning

When you open a file, a file pointer indicates the current position for reading or writing.

• The pointer starts at the beginning in modes like r and w.
• In append mode a, it starts at the end.

Python provides methods to manage the pointer:

• f.tell() returns the current position.
• f.seek(offset, whence) moves the pointer to a specified position.

Example:

``python f = open("file.txt", "r") print(f.tell()) # Prints 0 at start f.read(5) # Reads first 5 characters print(f.tell()) # Prints 5, pointer moved f.seek(0) # Moves pointer back to start f.close() ``

Managing the file pointer is useful for reading or writing at specific positions.

Comparison of File Handling Modes in Python

Here is a quick comparison of common file modes to help you choose the right one:

Use this table to avoid accidental data loss and to perform correct file operations.

Worked Example: Creating and Reading a Text File in Python

Let's create a simple text file, write data, and then read it.

```python # Create and write to a file f = open("student.txt", "w") f.write("Name: Rahul\nClass: 12\nSubject: Computer Science") f.close()

# Read the file content f = open("student.txt", "r") content = f.read() print(content) f.close() ```

Output: `` Name: Rahul Class: 12 Subject: Computer Science ``

This example demonstrates basic file handling operations covered in Class 12 NCERT syllabus.