How can you determine that a directory contains a Python module in the form of a package?

A directory is considered a Python package if it contains an __init__.py file. This file can be empty, but its presence indicates to the Python interpreter that the folder is a package and modules can be imported from it.

Example package structure:

my_package/
├── __init__.py
├── module1.py
└── subpackage/
    ├── __init__.py
    └── module2.py

Without the __init__.py file, Python 3.3+ supports namespace packages, but for a traditional package, this file is mandatory.