Expense_Tracker_fixes

[Sandhiya-003]

Description

This PR significantly enhances the basic ExpenseTracker script by fixing category tracking logic and introducing robust features like data persistence, input validation, budgeting limits, comprehensive search/filtering, and CSV exporting. It also refactors the code structure to follow Python best practices.

Fixes & Enhancements

• Bug Fixes: Corrected the category logic so that viewing categories dynamically reads and displays all added categories rather than just relying on active expenses.
• Data Persistence: Added save_data() and load_data() using a local JSON file (expenses_data.json) so user data survives application restarts.
• Input Validation: Implemented strict format checks for dates (YYYY-MM-DD with an option to default to today's date) and forced numeric validation for expense amounts to prevent system crashes.
• Budget Tracking: Added optional budget limits per category, featuring proactive warnings at 80% usage and alerts when limits are exceeded.
• CRUD Operations: Users can now seamlessly edit or delete specific expenses, as well as clear entire categories with confirmation prompts.
• Advanced Reporting & Search: Added powerful filters (by category, date range, or description keywords), monthly summaries, and visual CLI bar charts.
• Data Export: Integrated an export_to_csv() feature to export logs into spreadsheet-ready files.
• UI/UX Refactor: Upgraded the command-line interface with clean box-drawn menus, emoji indicators, aligned data tables, and structured the runtime logic using a standard if __name__ == "__main__": guard.

How to Test

1. Run the script: python expense_tracker.py
2. Try adding an expense with an invalid date format or text for the amount to verify the validation loops.
3. Add a category budget limit and log expenses to trigger the 80% and 100% threshold alerts.
4. Close the application and restart it to verify that data correctly reloads from expenses_data.json.
5. Run the CSV export option and check the generated file.

Checklist

• Code follows the style guidelines of this project
• My modifications do not break existing base functionality
• I have tested the script thoroughly locally
• Documented all new functions and methods with clean docstrings