refi-calculator 0.1.0

Refi Calculator Package.

Refi-Calculator

Refi-Calculator helps borrowers analyze whether refinancing makes sense by comparing current and proposed loan terms through breakeven, NPV, amortization, and holding-period views inside a Tkinter GUI.

Features

• Side-by-side analysis of current vs. proposed mortgage payments (nominal and after-tax)
• Breakeven and holding-period tables with clear recommendations
• Accelerated payoff planning for maintaining current payment levels
• Visual amortization comparisons plus cumulative savings (nominal/NPV) chart
• Exportable CSV data for every tab

Getting Started

Requirements

• Python 3.13+
• Poetry for dependency management (the virtual environment lives in .venv/)

Installation

poetry install

This command creates the virtual environment, installs dependencies, and prepares the hooks defined in .pre-commit-config.yaml.

Running the GUI

poetry run python bin/refi-calculator.py

The script boots the Tkinter application (src/refi_calculator/ui/app.py) that ties together all the analysis helpers.

Testing & Quality

• poetry run pre-commit run --all-files (runs formatting, linting, safety hooks, etc.)
• poetry run pytest (not yet populated, but ready for future tests)

Add new tests under tests/ following the test_*.py pattern whenever you enhance functionality.

Code Structure

• src/refi_calculator/models.py: Dataclasses for LoanParams and RefinanceAnalysis.
• src/refi_calculator/calculations.py: All refinance math helpers (NPV, amortization, sensitivity, etc.).
• src/refi_calculator/ui/: Tkinter GUI composed of:
  • app.py: The main application wiring.
  • chart.py: Custom savings chart canvas.
  • builders/: Tab-specific builders and helpers for clean separation of UI concerns.
• bin/refi-calculator.py: Entry point that runs the GUI.

Contributing

• Keep imports grouped by functionality (allow isort to do the heavy lifting through pre-commit).
• Update or add tests in tests/ before opening a pull request.
• Run poetry run pre-commit run --all-files to catch formatting/lint issues early.

License

See LICENSE.txt for licensing details.