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Chapter 2: File Handling in Python 🚀

Mentor's Note: Usually, a program's memory is like a dream—it vanishes when you wake up (close the program). File Handling is how we write things down in a diary so the computer remembers them forever! 💡

🌟 The Scenario: The Digital Filing Cabinet 🗄️

Imagine you are a clerk in a busy government office.

  • The Data: You have hundreds of applications (Data in variables). 📦
  • The File: You don't want to hold them in your hands all day. You put them into a Folder (The File) and store it in a Cabinet (The Hard Drive). 📦
  • The Result: Even if you go home and come back tomorrow, the data is still there! This is Persistence. ✅

📖 Concept Explanation

1. Types of Files

File Type Analogy Python Module
Text Files A handwritten letter ✉️ Built-in (open)
Binary Files A encrypted safe 🔐 pickle
CSV Files A simple spreadsheet 📊 csv

2. File Modes (The "Action" code)

  • 'r': Read (Open to look).
  • 'w': Write (Starts fresh, deletes old content!). ⚠️
  • 'a': Append (Adds to the end). ➕

🎨 Visual Logic: The File Lifecycle

graph LR
    A[Open File 📂] --> B[Read/Write ⚙️]
    B --> C[Close File 🔒]

    style C fill:#f96,stroke:#333

💻 Implementation: The Logging Lab

```python

🛒 Scenario: Keeping a Daily Journal

🚀 Action: Appending text to a file

Using 'with' is best practice (Auto-closes!) 🔒

with open("diary.txt", "a") as f: f.write("Today I learned Python File Handling! 🐍

") f.write("It was easier than I thought. ✅ ")

print("Journal updated!")
```

# 🛒 Scenario: Saving a Game High Score
import pickle

# 🚀 Action: Dumping an object into binary
data = {"player": "Vishnu", "score": 999}

with open("save.dat", "wb") as f:
    pickle.dump(data, f)

🧠 Step-by-Step Logic

  1. Start 🏁
  2. Open: Connect the program to the file using open().
  3. Mode: Specify if you are reading or writing.
  4. Action: Use .read(), .write(), or pickle.load().
  5. Close: Disconnect the file to save energy and memory.
  6. End 🏁

📊 Sample Dry Run (Read)

File content: "Hi Bye"

Turn Method Result Pointer Position
1 .readline() `"Hi
"` End of line 1 📍
2 .readline() "Bye" End of file 📍

📉 Technical Analysis

  • The Pointer: Python uses a "Cursor" (File Pointer) to track where it is in the file. ☝️
  • Performance: Reading line-by-line is memory-efficient for huge files. 🏎️

🎯 Practice Lab 🧪

Task: The Word Counter

Task: Write a program that reads a file story.txt and counts how many times the word "Python" appears. Hint: content.count("Python"). 💡

💡 Board Exam Focus (CBSE Class 12) 👔

  • Important: You will almost certainly get a question on writelines() vs write().
  • Answer: write() takes one string; writelines() takes a list of strings!

💡 Pro Tip: "Data is what you need to do analytics. Information is what you need to do a business." - John Cann

📈 Learning Path