File Handling Capstone Projects

# =========================================================================
# PROJECT 1: FILE-BASED TIMESTAMPED NOTES APPLICATION
# =========================================================================
import datetime as dt
from pathlib import Path

NOTES_FILE = Path("daily_notes.txt")

def add_note(note_text):
    """Append a new note with timestamp."""
    timestamp = dt.datetime.now().strftime("%Y-%m-%d %H:%M:%S")
    with open(NOTES_FILE, "a", encoding="utf-8") as f:
        f.write(f"[{timestamp}] {note_text.strip()}\n")
    return "✅ Note saved successfully!"

def view_all_notes():
    """Read and display all notes from file."""
    if not NOTES_FILE.exists():
        return "ℹ️ No notes recorded yet."
    with open(NOTES_FILE, "r", encoding="utf-8") as f:
        return f.read().strip()

def search_notes(keyword):
    """Search for notes containing a specific keyword."""
    if not NOTES_FILE.exists():
        return []
    matches = []
    with open(NOTES_FILE, "r", encoding="utf-8") as f:
        for line in f:
            if keyword.lower() in line.lower():
                matches.append(line.strip())
    return matches

# Run Notes App Demonstration:
print("--- 📝 Notes Application Demo ---")
add_note("Studied Python Exception Handling (try-except-else-finally)")
add_note("Built CSV Expense Tracker with DictReader")
add_note("Reviewing FastAPI background tasks for production")

print("\n--- All Saved Notes ---")
print(view_all_notes())

print("\n--- Search Results for 'Python' ---")
for note in search_notes("Python"):
    print("•", note)

# =========================================================================
# PROJECT 2: FILE-BACKED CONTACT BOOK APPLICATION
# =========================================================================
import json
from pathlib import Path

CONTACTS_FILE = Path("contacts_db.json")

def load_contacts():
    """Load contacts from JSON file safely."""
    if not CONTACTS_FILE.exists():
        return {}
    try:
        with open(CONTACTS_FILE, "r", encoding="utf-8") as f:
            return json.load(f)
    except (json.JSONDecodeError, OSError):
        return {}

def save_contacts(contacts_dict):
    """Save contacts dictionary to JSON file."""
    with open(CONTACTS_FILE, "w", encoding="utf-8") as f:
        json.dump(contacts_dict, f, indent=4)

def add_contact(name, phone, email, category="Personal"):
    """Add or update a contact record."""
    contacts = load_contacts()
    contacts[name.strip().title()] = {
        "phone": phone.strip(),
        "email": email.strip().lower(),
        "category": category
    }
    save_contacts(contacts)
    return f"✅ Contact '{name}' saved successfully!"

def search_contact(search_term):
    """Find contact by name substring or phone."""
    contacts = load_contacts()
    results = {}
    for name, details in contacts.items():
        if search_term.lower() in name.lower() or search_term in details["phone"]:
            results[name] = details
    return results

# Run Contact Book Demonstration:
print("--- 📱 Contact Book Manager Demo ---")
add_contact("Balaji Dev", "+91 98765 43210", "balaji@example.com", "Work")
add_contact("Alex Smith", "+1 555 123 4567", "alex@example.com", "Friends")
add_contact("Chloe Davis", "+44 20 7946 0991", "chloe@techcorp.com", "Work")

print("\n--- Search Results for 'balaji' ---")
print(json.dumps(search_contact("balaji"), indent=2))

# =========================================================================
# PROJECT 3: FINANCIAL EXPENSE TRACKER USING CSV
# =========================================================================
import csv
import datetime as dt
from pathlib import Path

EXPENSES_FILE = Path("monthly_expenses.csv")
FIELDNAMES = ["date", "category", "description", "amount"]

def initialize_expense_file():
    """Ensure CSV file exists with proper headers."""
    if not EXPENSES_FILE.exists():
        with open(EXPENSES_FILE, "w", newline="", encoding="utf-8") as f:
            writer = csv.DictWriter(f, fieldnames=FIELDNAMES)
            writer.writeheader()

def log_expense(category, description, amount):
    """Log an expense entry to CSV."""
    initialize_expense_file()
    entry = {
        "date": dt.date.today().isoformat(),
        "category": category.title(),
        "description": description.strip(),
        "amount": f"{float(amount):.2f}"
    }
    with open(EXPENSES_FILE, "a", newline="", encoding="utf-8") as f:
        writer = csv.DictWriter(f, fieldnames=FIELDNAMES)
        writer.writerow(entry)
    return f"✅ Logged Rs.{float(amount):.2f} for '{description}'"

def generate_expense_analytics():
    """Calculate total spending and category breakdown."""
    if not EXPENSES_FILE.exists():
        return 0.0, {}
        
    total_spent = 0.0
    category_totals = {}
    
    with open(EXPENSES_FILE, "r", encoding="utf-8") as f:
        reader = csv.DictReader(f)
        for row in reader:
            amt = float(row["amount"])
            cat = row["category"]
            total_spent += amt
            category_totals[cat] = category_totals.get(cat, 0.0) + amt
            
    return round(total_spent, 2), category_totals

# Run Expense Tracker Demonstration:
print("--- 💰 Financial Expense Tracker Demo ---")
log_expense("Food", "Grocery Supermart Shopping", 1250.00)
log_expense("Utilities", "High-Speed Internet Bill", 999.00)
log_expense("Food", "Team Coffee & Snacks", 350.00)
log_expense("Education", "Python Masterclass Subscription", 1499.00)

total, breakdown = generate_expense_analytics()
print(f"\n📊 Total Monthly Expenditure: Rs.{total:,.2f}")
print("--- Category Breakdown ---")
for cat, amt in breakdown.items():
    pct = (amt / total) * 100 if total > 0 else 0
    print(f"• {cat:12}: Rs.{amt:,.2f} ({pct:.1f}%)")

# =========================================================================
# PROJECT 4: JSON STUDENT ACADEMIC RECORDS SYSTEM
# =========================================================================
import json
from pathlib import Path

STUDENT_DB = Path("students_database.json")

def load_db():
    if not STUDENT_DB.exists(): return {"students": {}}
    with open(STUDENT_DB, "r", encoding="utf-8") as f:
        return json.load(f)

def save_db(data):
    with open(STUDENT_DB, "w", encoding="utf-8") as f:
        json.dump(data, f, indent=4)

def register_student(student_id, name, branch):
    """Create a new student profile."""
    db = load_db()
    if student_id in db["students"]:
        return f"❌ Student ID {student_id} already exists!"
        
    db["students"][student_id] = {
        "name": name,
        "branch": branch,
        "marks": {},
        "gpa": 0.0
    }
    save_db(db)
    return f"🎓 Student '{name}' registered successfully under ID: {student_id}"

def record_marks(student_id, subject, score):
    """Add subject score and recalculate GPA."""
    db = load_db()
    student = db["students"].get(student_id)
    if not student:
        return f"❌ Student {student_id} not found!"
        
    student["marks"][subject] = score
    all_scores = list(student["marks"].values())
    student["gpa"] = round(sum(all_scores) / len(all_scores), 2)
    save_db(db)
    return f"✅ Recorded {subject}: {score}/100 | New GPA: {student['gpa']}"

def get_student_report_card(student_id):
    """Generate a clean formatted report card."""
    db = load_db()
    student = db["students"].get(student_id)
    if not student: return "Student not found!"
    
    lines = [
        "=" * 45,
        f"📋 REPORT CARD: {student['name']} (ID: {student_id})",
        f"Branch: {student['branch']} | Overall GPA: {student['gpa']}%",
        "-" * 45,
        "Subject Scores:"
    ]
    for sub, mark in student["marks"].items():
        lines.append(f"  • {sub:20}: {mark}/100")
    lines.append("=" * 45)
    return "\n".join(lines)

# Run Student Records Demonstration:
print("--- 🎓 Student Records Management System ---")
register_student("STU101", "Balaji", "Computer Science")
record_marks("STU101", "Python Programming", 98)
record_marks("STU101", "Data Structures", 92)
record_marks("STU101", "Database Systems", 95)

print(get_student_report_card("STU101"))