Pip install sub-package from own (namespace) package in python

Question

I'd like to install some special sub-package from a package.

For example, I want to create package with pkg_a and pkg_b. But I want to allow the user to choose which he wants to install.

What I'd like to do:

git clone https://github.com/pypa/sample-namespace-packages.git
cd sample-namespace-packages
touch setup.py

setup-py:

import setuptools

setup(
    name='native',
    version='1',
    packages=setuptools.find_packages()
)

# for all packages
pip install -e native #Successfully installed native

# for specific
# Throws ERROR: native.pkg_a is not a valid editable requirement. 
# It should either be a path to a local project
pip install -e native.pkg_a native.pkg_b

# for specific
cd native
pip install -e pkg_a # Successfully installed example-pkg-a

I've seen this in another questions answer so it must be possible: Python install sub-package from package

Also I've read the Packaging namespace packages documentation and tried to do the trick with the repo

I've tried some variants with an additional setup.py in the native directory, but I can't handle it and I am thankful for all help.

Update

In addition to the answer from sinoroc I've made an own repo. I created a package Nmspc, with subpackages NmspcPing and NmspcPong. But I want to allow the user to choose which he wants to install. Also it must to be possible to install the whole package.

What I'd like to do is something like that:

git clone https://github.com/cj-prog/Nmspc.git
cd Nmspc

# for all packages
pip install Nmspc

# Test import
python3 -c "import nmspc; import nmspc.pong"

# for specific
pip install -e Nmspc.pong # or 
pip install -e pong

# Test import
python3 -c "import pong;"

Answer 1

If the projects are not installed from an index such as PyPI, it is not possible to take advantage of the install_requires feature. Something like this could be done instead:

.
├── NmspcPing
│   ├── nmspc.ping
│   │   └── __init__.py
│   └── setup.py
├── NmspcPong
│   ├── nmspc.pong
│   │   └── __init__.py
│   └── setup.py
└── setup.py

NmspcPing/setup.py (and similarly NmspcPong/setup.py)

import setuptools

setuptools.setup(
    name='NmspcPing',
    version='1.2.3',
    package_dir={'nmspc.ping': 'nmspc.ping'},
    packages=['nmspc.ping'],
)

setup.py

import setuptools

setuptools.setup(
    name='Nmspc',
    version='1.2.3',
    package_dir={
        'nmspc.ping': 'NmspcPing/nmspc.ping',
        'nmspc.pong': 'NmspcPong/nmspc.pong',
    },
    packages=['nmspc.ping', 'nmspc.pong'],
)

This allows to install from the root folder in any of the following combinations:

$ python3 -m pip install .
$ python3 -m pip install ./NmspcPing
$ python3 -m pip install ./NmspcPong
$ python3 -m pip install ./NmspcPing ./NmspcPong