One simple calculator, taken from first design to best practice.

The walkthrough

Follow the notebooks in order — each revisits the same calculator with higher standards. Open any notebook directly in Google Colab (no install) or read it in nbviewer.

• calculator_design.ipynbThe challenge and the design — start hereColabnbviewer
• calculator_good_development.ipynbA good first working version, development styleColabnbviewer
• calculator_good_production.ipynbThe same version, cleaned up for productionColabnbviewer
• calculator_better.ipynbBetter structure: functions, validation, exceptionsColabnbviewer
• calculator_better_production.ipynbThe better version, production-readyColabnbviewer
• calculator_best.ipynbThe best-practice version — the full walkthrough with notesColabnbviewer
• calculator_eval.ipynbEvaluating the versions against each otherColabnbviewer

Supporting modules

The later versions factor code into modules, built in their own notebooks: my_math, user_interface, and utilities.

The ten best practices

The habits the walkthrough applies, version by version:

1. Use a code repository — small, frequent commits
2. Follow style guidelines (PEP 8)
3. Correct broken code immediately — exceptions, validation, testing
4. Use PyPI instead of reinventing — import it
5. Use the right data types and structures
6. Write readable code — meaningful names and comments
7. Create readable documentation — docstrings
8. Use virtual environments
9. Avoid anti-patterns — specific imports, specific exceptions
10. Follow the Zen of Python — try import this