How to write your __init__.py

What should you put into your __init__.py?

Perhaps you already know that a python package is a directory which contains a __init__.py file
In this article we will solve the mystery around the __init__.py

For this article let’s assume the following project structure:

Empty init file

Sometimes doing nothing isn’t so bad at all. You can of course leave the init file empty

That means that you have to import func_a from module_a in package_a in the follow way from your main.py

from package_a.module_a import func_a 

func_a()

Import * in init

If you want to avoid giving the the full path to your function you can place an import statement in the __init__.py as well

from .module_b import *

In your main.py you don’t have to mention the module name anymore:

from package_b import func_b 

func_b()

__all__ list

In addition to adding an import in your init file you can also add the __all__ list declaration

With this construct you can decide which functions from your modules will be imported when you use the “import *” semantic:

__all__ = ['func_c'] 
from .module_c import *

In main.py

from package_c import * 

func_c() # working 
func_d() # not working! Unresolved reference 'func_d'

This is excellent for API design to describe which functions shall be exposed to the user of the package.