Topic 11. Modules and packages, working with files (pathlib, JSON, CSV), and unit testing with pytest

Goal: learn to organize code across modules, work with paths and structured files, create console commands, and test them automatically with pytest.

Lecture contents

1. Modules, packages, and the entry point — Modules and imports · Packages and the entry point
2. Paths and text files — Paths and pathlib file operations · Text files and encoding
3. JSON and CSV — JSON and the stored-data contract · CSV as a table of text fields
4. Unit testing with pytest — Unit tests and pytest · Fixtures, dependencies, and test diagnostics · Project configuration and running in PyCharm · Common mistakes and finishing the work

Practice and review

• Practice — 3 worked examples with complete code
• Tasks — 30 variants, each with tasks at three difficulty levels
• Summary — conclusions, self-check questions, and useful links