How to write nested init.py files

I am struggling with nested __init__.py in a Python package I am writting. The Package has the following architecture:

module/
├── __init__.py
├── submodule1
│   ├── __init__.py
│   └── source.py
└── submodule2
    ├── __init__.py
    ├── source.py
    └── subsubmodule2
        ├── __init__.py
        └── source.py

My intent is to be able to access functions defined in submodule2/source.py through module.submodule2.function and in subsubmodules2/source.py through module.submodule2.subsubmodule2.function.

The first thing I tried was to define __init__.py in submodule2 this way:

from .subsubmodule2 import *

But doing so, I get the functions defined in subsubmodules2/source.py through module.submodule2.function (and module.function).

If I do:

from . import subsubmodule2

I get these functions through module.subsubmodule2.function.

I also tried to define __all__ keyword in __init__, with no more success. If I understand well Python documentation, I guess I could leave empty __init__.py files and it could work, but from my understanding that is not the best practice either.

What would be the best way to access these functions as intended in my module?

Solution

in module __init__.py file write the module which you want to import as

from . import submodule1
from . import submodule2
__all__ = ['submodule1', 'submodule2']

Now, in submodule1 __init__.py file write

from . import source
from . import subsubmodule
# if you want to import functions from source then import them or in source.py
# define __all__ and add function which you want to expose
__all__ = ['source', 'subsubmodule']

now in subsubmodule __init__ file define function or class which you want to expose

from . source import *
__all__ =  ['source']
# if you want to use * as import, i suggest you to use __all__ in source.py and mention all exposed function there

How to write nested __init__.py files

How to write nested init.py files