Intra-package reference of modules in sub-packages using dotted syntax

Question

I have the following package structure:

.
└── package
    ├── __init__.py
    ├── sub_package_1
    │   ├── __init__.py
    │   └── main_module.py
    ├── sub_package_2
    │   ├── __init__.py
    │   └── some_module.py
    └── sub_package_3
        ├── __init__.py
        └── some_module.py

In package/sub_package_1/main_module.py I want to use both package/sub_package_2/some_module.py and package/sub_package_3/some_module.py . For this I want to use intra-package reference . I know that I can use from ..sub_package_1 import some-module but because of the similar name I want to use dotted syntax such as sub_package_1.some_module .

Using from .. import sub_package_2 I obviously cannot access sub_package_2.some_module because sub_package_2 is a package. However I found out that using

from .. import sub_package_2
from ..sub_package_2 import some_module

I can access sub_package_2.some_module . Apparently the 2nd import adds some_module to sub_package_2 (checking dir(sub_package_2) ).

My questions are:

1. Is there a way to use a single import instead of the two above?
2. Why does (in general) import package followed by from package import module add module to package ? What is Python actually doing here?

Answer 1

1.

In the file __init__.py of sub_package_2 you write

from . import some_module

And in main_module.py you can must write

from .. import sub_package_2

And the code sub_package_2.some_module should work now

2.

"How import in python work" you can read more here Importing Python Modules

from .. import sub_package_2 creates a reference to sub_package_2 in the current namespace. Package sub_package_2 is like a module now and is defined in the file __init__.py . If you wrote nothing in __init__.py , sub_package_2 won't know some_modue

from ..sub_package_2 import some_module create a reference to the module some_module of the package sub_package_2 with the name some_module . It's something like some_module = sub_package_2.some_module . You see: there are a reference to some_module in sub_package_2 too. And now sub_package_2 knows the module some_module

Important: You can use sub_package_2.some_module but only some_module will work too. They are identical after your 2 imports.

And if you write in the __init__.py :

from . import some_module

some_module belongs to sub_package_2 automatically

For similar module names you can use as

from ..sub_package_1 import some_module as some_module_1
from ..sub_package_2 import some_module as some_module_2
from ..sub_package_3 import some_module as some_module_3