File Handling in Python: A Comprehensive Guide, Lecture notes of Programming Languages

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File Handling in

Programming: Read,

Write, and Manage

Files in Python

Table of Contents

1. Introduction
2. Why File Handling Matters
3. Opening a File
4. Reading from a File

5. Writing to a File
6. Appending to a File
7. Closing a File
8. Using with Statement
9. Common Errors and Debugging
10. Practice Questions
11. Summary

📘 1. Introduction

In real-world programming, we often need to store data permanently —like saving student records, logs, or results. That’s where file handling comes in. Python makes it easy to read , write , and update files using simple commands. Whether it's a .txt, .csv, or .json file, mastering file handling is essential for building real applications. 🗒 Sticky Note : File handling = talking to your computer’s memory. You read from it, write to it, and save your work.

📘 2. Why File Handling Matters

 Store data between program runs  Save user input, logs, or reports  Read configuration files

📘 Example: python file = open("data.txt", "r") content = file.read() print(content) file.close() 📘 Other Methods:  readline() → reads one line  readlines() → reads all lines as a list 🗒 Quick Tip : Use .strip() to remove extra spaces or newline characters.

✍️ 5. Writing to a File

📘 Example: python file = open("data.txt", "w") file.write("Hello, Zano!") file.close() 📘 Explanation:  "w" mode overwrites the file  Use \n to add new lines 🗒 Sticky Note :

"w" mode erases old content. Use "a" if you want to keep it.

📘 6. Appending to a File

📘 Example: python file = open("data.txt", "a") file.write("\nNew line added.") file.close() 🗒 Quick Tip : Appending is useful for logs, history, or adding new entries.

📘 7. Closing a File

Always close the file after you're done to free system resources. python file.close() 🗒 Sticky Note : Think of closing a file like shutting a notebook—don’t leave it open!

📘 9. Common Errors and Debugging

Error Type Cause Fix FileNotFoundError File doesn’t exist Check filename or path IOError File is locked or unreadable Use correct mode and permissions ValueError Wrong mode or operation Match method with mode 🗒 Quick Tip : Use try-except blocks to handle errors gracefully.

🧪 10. Practice Questions

1. Write a program to read a file and print its contents
2. Create a file and write 5 student names
3. Append a new name to the file
4. Use with statement to read a file
5. Handle FileNotFoundError using try-except

📘 11. Summary

 Use open() with correct mode ("r", "w", "a")  Always close() the file or use with  Use read(), write(), append() based on your task  Handle errors with care