# What is init.py for?

In Python, the `__init__.py` file is used to mark a directory as a Python package. It is used to initialize the package when it is imported.

The `__init__.py` file can contain code that will be executed when the package is imported, as well as function definitions and variable assignments. It is a good place to put any code that you want to run when the package is first imported.

For example, suppose you have a package called `mypackage` with the following structure:

```
mypackage/
    __init__.py
    module1.py
    module2.py
    ...
```

If you want to import `module1` from `mypackage`, you can do so using the following import statement:

```python
import mypackage.module1
```

When you run this import statement, Python will execute the code in `__init__.py` before it executes the import statement for `module1`. This can be useful if you want to do some initialization or setup before the other modules in the package are imported.

It is also possible to have multiple levels of packages, with `__init__.py` files at each level. For example:

```
mypackage/
    __init__.py
    subpackage1/
        __init__.py
        module1.py
        module2.py
        ...
    subpackage2/
        __init__.py
        module1.py
        module2.py
        ...
```

In this case, you would import a module from `subpackage1` using the following import statement:

```python
import mypackage.subpackage1.module1
```

Again, the code in the `__init__.py` files for `mypackage` and `subpackage1` would be executed before the import statement for `module1` is executed.

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