packages.md

Python by Example: Packages

A package is a directory containing an __init__.py file and one or more modules. It organizes related code into a namespace. Use dot notation to import: from mypackage.utils import greet. The __init__.py can be empty or run package setup. Packages are the standard way to structure larger projects.

What you'll learn:

• Package structure and __init__.py
• Importing from packages
• How Python finds packages via sys.path

Standard layout:

mypackage/
  __init__.py      # marks directory as package; can be empty
  utils.py         # module inside package
  models.py        # another module

Create a minimal package and import from it:

import tempfile
import sys
from pathlib import Path

# Create a temp package structure
tmp = Path(tempfile.mkdtemp())
pkg = tmp / "mypackage"
pkg.mkdir()

(pkg / "__init__.py").write_text("")
(pkg / "utils.py").write_text('def greet(name):\n    return f"Hello, {name}!"\n')

# Add to path and import
sys.path.insert(0, str(tmp))
from mypackage.utils import greet
print(greet("World"))

We create a temporary package on disk, add it to sys.path, and import. In a real project, the package lives in your project directory or in site-packages.

To run this program:

$ python source/packages.py
Hello, World!

Tip: In Python 3.3+, namespace packages don't require __init__.py in every directory, but explicit packages are still the norm.

Try it: Create a mypackage folder with __init__.py and a module, then import from it.

Source: packages.py

Next: Async Basics