Relational Expense Tracker & Financial Management Utility

A structured, production-grade Python CLI backend ledger designed to track, categorize, and calculate transactional financial data. This project transitions standard flat-file data persistence (CSV) into a robust, relational database architecture using SQLite.

🚀 Engineered Enhancements

• Relational Storage: Migrated from volatile string-parsing file inputs (.csv) to a normalized database schema, ensuring data integrity across application lifetimes.
• Algorithmic & Database Efficiency: Delegated computational grouping and summing from application memory ($O(N)$ runtime) to the SQL engine using optimized SUM and GROUP BY data aggregations.
• Security & Exploitation Prevention: Implemented fully parameterized queries (? placeholders) to completely mitigate SQL Injection vulnerabilities from user console entries.
• Defensive Input Validation: Built robust try-except validation execution loops to handle malformed, out-of-bounds, or non-numeric entries gracefully, guaranteeing zero application crashes.
• Centralized Data Layer: Developed a modular query runner utilizing Python context managers (with statements) to securely handle database connections, cursor tracking, auto-committing, and resource teardown.

📊 Database Architecture (Schema)

The SQLite engine enforces a strict schema for transaction validation:

• id (INTEGER, Primary Key, Auto-Increment) - Unique row identifier.
• name (TEXT, Not Null) - The text description of the transaction.
• amount (REAL, Not Null) - Numeric floating-point transaction value.
• category (TEXT, Not Null) - Categorical string label.
• date (TEXT, Default CURRENT_TIMESTAMP) - Automated chronological log entry.

🛠️ Tech Stack & Concepts Applied

• Language: Python 3.11+
• Database Engine: SQLite 3
• Core Concepts: Parameterized Queries, Relational Schemas, Computational Aggregations, Context Managers, Defensive Programming.

🏃‍♂️ Core Features & Interface

The interactive command-line interface provides users with an entry menu to manage transactional workflows:

1. ➕ Add New Expense: Instantiates a secure record transaction and dynamically tracks category metrics.
2. 📜 View Complete History: Queries individual data records sequentially, descending by chronological timestamp.
3. 📊 View Metric Aggregations: Evaluates real-time financial tracking statistics, including categorical overviews, absolute totals, and variable daily budget burn-rates based on the remaining calendar days in the month.

How to Run Locally

1. Clone the repository:

   git clone [https://github.com/YOUR_USERNAME/Expense-app.git](https://github.com/YOUR_USERNAME/Expense-app.git)
   cd Expense-app