Customizing python package directory layout with setup.py

Suppose I have the following directory structure:

src/
└── python/
    └── generated/
        ├── __init__.py
        ├── a.py
        └── lib/
            ├── __init__.py
            └── b.py

What does my setup.py need to look like in order to create a dist with a directory layout like:

src/
└── python/
    ├── __init__.py
    ├── a.py
    └── lib/
        ├── __init__.py
        └── b.py

The goal is to simply eliminate the generated folder. I've tried endless variations with package_dir and can't get anything produced other than the original directory structure.

In this specific case, for this specific project directory structure, the setup.py script should be placed in the src directory and should look like this:

#!/usr/bin/env python
    
import setuptools
    
setuptools.setup(
    name='Thing',
    version='1.2.3',
    packages=[
        'python',
        'python.lib',
    ],
    package_dir={
        'python': 'python/generated',
    },
)

Note the package_dir setting. It instructs setuptools to get the code for the python package from the directory python/generated. In the built distributions you will then find the right directory structure.