What is __init__.py for?

Explanation

If you have the following files. So the files name with __init__.py are used to mark directories on disk as Python package directories. 

mydir/spam/__init__.py
mydir/spam/module.py

and mydir is on your path, you can import the code in module.py as

import spam.module

or you can also write as :

from spam import module

Attempts will get fail if you try to import the module. Python will no longer look for submodules inside that directory If you remove the __init__.py file.

Generally, __init__.py file is usually empty. But under the more convenient name, you can use export selected portions of the package 

Also read, How to concatenate string variables in Bash