Project - Personal Budget Tracker :

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Managing personal finances is an essential life skill. Many people struggle to track their income and expenses, which leads to overspending or missed savings goals. In this project, you’ll build a Personal Budget Tracker in Python that allows users to log their income and expenses, categorize transactions, and get summaries of their financial activity.

Users should be able to:

Add transactions (income or expense)
Categorize each transaction (e.g., “Food”, “Rent”, “Salary”)
Automatically include the current date
View their total balance
Get summaries by month and category
Save and load data using a JSON file so the information persists across sessions

You’ll apply object-oriented programming, basic file I/O, JSON, and input validation. This project will help you learn how to structure real-world applications in Python and prepare your code for scaling or adding features like exporting data or using a graphical interface.

📌 Main Objectives

Create a class for individual transactions
Create a class to manage all financial operations
Add and categorize income and expenses
Automatically date transactions
Save all data in a JSON file
View balance and summaries by month
Handle invalid inputs with error messages
Use clean and modular OOP code

✅ Solution :

import json
import os
from datetime import datetime
from collections import defaultdict

# Represents a single income or expense transaction
class Transaction:
    def __init__(self, amount, category, t_type, date=None):
        self.amount = amount
        self.category = category
        self.t_type = t_type  # 'income' or 'expense'
        self.date = date if date else datetime.now().strftime("%Y-%m-%d")

    def to_dict(self):
        return {
            "amount": self.amount,
            "category": self.category,
            "type": self.t_type,
            "date": self.date
        }

    @staticmethod
    def from_dict(data):
        return Transaction(
            amount=data['amount'],
            category=data['category'],
            t_type=data['type'],
            date=data['date']
        )

# Manages the collection of transactions and user operations
class BudgetTracker:
    def __init__(self, filename="budget_data.json"):
        self.filename = filename
        self.transactions = []
        self.load_data()

    def add_transaction(self, amount, category, t_type):
        if t_type not in ["income", "expense"]:
            print("❌ Invalid type. Use 'income' or 'expense'.")
            return
        transaction = Transaction(amount, category, t_type)
        self.transactions.append(transaction)
        self.save_data()
        print(f"✅ Added {t_type} of {amount} in category '{category}'.")

    def show_balance(self):
        income = sum(t.amount for t in self.transactions if t.t_type == "income")
        expenses = sum(t.amount for t in self.transactions if t.t_type == "expense")
        print(f"💰 Total Income: {income}")
        print(f"💸 Total Expenses: {expenses}")
        print(f"📊 Balance: {income - expenses}")

    def monthly_summary(self, year_month):
        summary = defaultdict(lambda: {"income": 0, "expense": 0})
        for t in self.transactions:
            if t.date.startswith(year_month):
                summary[t.category][t.t_type] += t.amount

        print(f"\n📅 Summary for {year_month}:")
        for category, totals in summary.items():
            print(f"{category}: +{totals['income']} | -{totals['expense']}")

    def save_data(self):
        with open(self.filename, 'w') as f:
            json.dump([t.to_dict() for t in self.transactions], f)

    def load_data(self):
        if not os.path.exists(self.filename):
            return
        with open(self.filename, 'r') as f:
            data = json.load(f)
            self.transactions = [Transaction.from_dict(d) for d in data]

# Simple CLI interface
def main():
    tracker = BudgetTracker()

    while True:
        print("\n=== Budget Tracker Menu ===")
        print("1. Add Income")
        print("2. Add Expense")
        print("3. Show Balance")
        print("4. Monthly Summary")
        print("5. Exit")

        choice = input("Choose an option: ")

        if choice == "1":
            try:
                amount = float(input("Enter amount: "))
                category = input("Enter category: ")
                tracker.add_transaction(amount, category, "income")
            except ValueError:
                print("⚠️ Invalid amount.")
        elif choice == "2":
            try:
                amount = float(input("Enter amount: "))
                category = input("Enter category: ")
                tracker.add_transaction(amount, category, "expense")
            except ValueError:
                print("⚠️ Invalid amount.")
        elif choice == "3":
            tracker.show_balance()
        elif choice == "4":
            year_month = input("Enter year and month (YYYY-MM): ")
            tracker.monthly_summary(year_month)
        elif choice == "5":
            print("👋 Goodbye!")
            break
        else:
            print("❌ Invalid option.")

if __name__ == "__main__":
    main()

📖 Concepts and Tools Used

OOP (Classes): Used to define clear structure (Transaction, BudgetTracker)
JSON: Used to store and load transaction data
Datetime: To add the current date automatically to each transaction
defaultdict: For grouped monthly summaries without worrying about missing keys
Error Handling: Basic try/except and input validation
File I/O: Reading/writing to a .json file for persistent storage