My final project for Harvard's CS50p - Introduction to Python:
This program has 4 main features:
- To retrieve & display current interest rates from (some) Canadian banks
- To determine the mortgage payment amount
- To calculate & display a complete amortization schedule
- To export the amortization schedule as a CSV file
These features are implemented as a graphical user interface using PySimpleGUI library. Interest rates are retrieved from bank websites using Scrapy - a web scraping library for Python. The pip install requirements are stated in requirements.txt.
The calculations update instantly when any relevant input value is changed.
The interest rate can be entered manually, as web-scraping is an optional feature. When Fetch Bank Rates is clicked, the Bank Rates table is populated. When selecting any row from Bank Rates table, the interest rate field is updated, and the payment and amortization schedules are re-calculated.
When Export to CSV is clicked, the user is prompted by a File Save dialog to select a path and file name. The amortization schedule is then saved to the specified file name.
# install dependencies
pip install scrapy
pip install PySimpleGUI
# run the program
python project.py
The program consists of 2 python modules, and a test module:
| File | Description |
|---|---|
| project.py | the main GUI and it's helper functions |
| spiders.py | the web scraping (spider) module |
| test_project.py | test cases for each function in project.py |
test_project.py contains 9 tests implemented with the PyTest testing framework. These tests exercise the helper functions in project.py. Each helper function has a happy-path test case, and "error" test case (non-happy path).
The PySimpleGUI library was chosen for it's ease of use and short learning curve. It comes with a huge number of examples provided by the community, which made it very easy to learn and create a simple GUI in a short time.
Scrapy library was chosen specifically because I wanted to learn about web-scraping. This is a powerful and complex library - it's overkill for what's being accomplished here. But was a good lesson in how to use it.