The __init__.py files are used to mark directories on the file system as Python package directories. If you have directories within a Python project and you want to import modules from them, you would typically include an __init__.py file in each directory to tell Python it is a package from which modules can be imported.

As of Python 3.3, thanks to the introduction of "namespace packages", the __init__.py files are no longer strictly required for this purpose. However, they are still widely used for several reasons:

1. Compatibility: If you want your code to be usable by people running versions of Python older than 3.3, you'll need to include __init__.py files.
2. Initializing Package State: Sometimes, you may want to perform some initialization when a package is imported. This could be setting up paths, logging, or other configuration that is package-specific. This initialization code goes in the __init__.py file.
3. Declaring the Public API: You can use the __init__.py file to neatly specify the public interface of your package. If you want to make some classes or functions available at the package level, you can define them in __init__.py, or use it to selectively import certain things from modules within the package.
4. Namespace Control: You can use __init__.py to control the internal namespaces of your package. This might involve using __all__ to restrict what gets imported when from <package> import * is used.

Here is an example of what might go in an __init__.py file:

# __init__.py

# Import some core modules into the package namespace
from .core_module import CoreClass, core_function

# Define an __all__ for import * control
__all__ = ['CoreClass', 'core_function', 'subpackage']

# Perhaps some package-level variables or objects
package_variable = 'This is a package variable'

# Any initialization code your package might need
def _initialize_package():
    # Some initialization logic
    pass

_initialize_package()

In this example, core_module might be a module in the same directory as the __init__.py file, and CoreClass and core_function are entities within that module that you want to be directly accessible when the package is imported.

If your packages don't need any specific initialization and you're using Python 3.3 or newer, you can leave __init__.py files empty, and they will still serve their basic purpose of marking the directories as Python packages.