Packages and Project Layout

A package is a directory of modules (historically one containing __init__.py). Packages give you dotted names and a place for shared setup:

# tasknoter/
#   pyproject.toml
#   src/
#     tasknoter/
#       __init__.py        # makes 'tasknoter' a package
#       storage.py
#       cli.py

from tasknoter.storage import load_tasks

The src/ layout (a package directory inside src/) is the packaging community's recommendation: it makes it impossible to accidentally import the local copy instead of the installed one, because tests run against the installed package.

Layering a growing application

Professional Python codebases tend to separate three concerns:

• domain — the data and rules (Task, complete(), validation). Knows nothing about IO.
• storage — saving/loading (files, sqlite). Talks to the domain.
• interface — CLI or web handlers. Talks to both, contains no business rules.

Arrows point one way: interface → domain ← storage. The moment your CLI function contains SQL and validation in the same 100 lines, tests get hard and changes get risky. Layering is what makes module 7's testing and the capstone enjoyable instead of painful.

Absolute vs relative imports

Inside a package prefer absolute imports (from tasknoter.storage import load). Relative imports (from .storage import load) work too but are a frequent source of confusion when files move. Pick absolute by default.