PEP 420 - implicit namespace packages

If you use and target only Python 3, then there is good news for you. PEP 420 (Implicit Namespace Packages) introduced a new way to define namespace packages. It is part of the standards track and became an official part of the language since version 3.3. In short, every directory that contains Python packages or modules (including namespace packages too) is considered a namespace package if it does not contain the __init__.py file. So, the following are examples of file structures presented in the previous section:

$ tree acme.sql/
acme.sql/
├── acme
│   └── sql
│       └── __init__.py
└── setup.py

2 directories, 2 files

$ tree acme.templating/
acme.templating/
├── acme
│   └── templating
│       └── __init__.py
└── setup.py

2 directories, 2 files

They are enough to define that acme is a namespace package under Python 3.3 and later. Minimal setup.py for acme.templating package will look like following:

from setuptools import setup
   
   
setup(
    name='acme.templating',
    packages=['acme.templating'],
)

Unfortunately, the setuptools.find_packages() function does not support PEP 420 at the time of writing this book. This may change in the future. Also, a requirement to explicitly define a list of packages seems to be a very small price to pay for easy integration of namespace packages.