Software Engineering with Python

Programme overview

Code that works once isn't software yet. In this course you rebuild Tallybook's invoicing code the way professional teams work. You'll turn a script into functions and modules, discover why floating-point numbers and Python's round() put 164 of 1,171 real invoices a kobo out, and fix it with whole kobo and Decimal. You'll write tests with pytest and run them in Colab, find an off-by-one bug in late fees with boundary tests, debug a crashing import by finding every bad row rather than one, and validate a messy export so every row is accounted for. Then you'll track changes with Git branches and commits, review the original billing module for both style problems and wrong business rules, and expose the rules as a Flask API that rejects bad requests clearly. Every command and test in the lessons is run and checked.

Curriculum

1. 01From Script to Functions15 min

   • From script to functionsWhy code that works once isn't yet software, how to turn a copy-and-paste script into small functions with clear inputs and outputs, and the first signs that the numbers it produces are wrong.
2. 02Money and Rounding15 min

   • Money and roundingWhy floating-point numbers and Python's round() are wrong for money, how to calculate in whole kobo with Decimal and round half up, and how many of Tallybook's real invoices the old way got wrong.
3. 03Modules and Tests15 min

   • Modules and testsMove the invoice rules into a module, write automated tests for them with pytest, and run the tests in Colab, so every change is checked in seconds instead of by hand.
4. 04Edge Cases and Boundaries15 min

   • Edge cases and boundariesDesign tests around boundaries, where most bugs live, use pytest's parametrize to check many cases at once, and find and fix an off-by-one bug in Tallybook's late fees.
5. 05Debugging15 min

   • DebuggingRead a traceback from the bottom up, narrow a failure down to the exact input that causes it, and use the data to find every row with the same problem, instead of fixing them one crash at a time.
6. 06Validating Input25 min

   • Validating inputCheck every record before using it, collect every problem with a clear reason instead of crashing on the first, and decide what happens to bad records so they're fixed rather than silently dropped.
7. 07Version Control with Git15 min

   • Version control with GitTrack every change to code with Git, make small commits with clear messages, work on a branch, read a diff, and merge, all with real commands in Colab.
8. 08Code Review25 min

   • Code reviewReview code for correctness, clarity and risk, use simple automated checks to find common problems, and write review comments that are specific, kind and actionable, on Tallybook's original billing module.
9. 09Building an API15 min

   • Building an APIExpose the invoice rules as a small web API with Flask, validate requests and return clear errors with the right status codes, and test the API without running a server.
10. 10Final Project20 min

    • Final project: Tallybook's invoicing servicePlan your final project, a tested, version-controlled invoicing package and API that replaces the old billing module, with every rule tested at its boundaries and every row of the export accounted for.

Assessment and certificate

You are assessed with a final assessment (pass mark 60%) and a final project. Your certificate is awarded when you meet those requirements. Paying for the programme does not award it on its own.